6 ms·

MCP Apps: Extending servers with interactive user interfaces

192 points by mercury24aug 10mo ago

mercury24aug 10mo ago
Looks like OpenAI, Anthropic, and the MCP-UI team actually worked together on a common standard for MCP Apps: https://blog.modelcontextprotocol.io/posts/2025-11-21-mcp-apps/ https://blog.modelcontextprotocol.io/posts/2025-11-21-mcp-ap... Honestly, I think the biggest friction for MCP adoption has been how un-userfriendly it is. It’s great for devs, but not the average users. Users don't always want to chat, sometimes they just want to click a button or adjust a slider. This feels like the answer to that problem. Full disclosure, I'm partial here because of our work at https://usefractal.dev https://usefractal.dev. We were early adopters when MCP first came out, but we always felt like something was missing. We kept wishing for a UI layer on top, and everyone says it's gonna take forever for the industry to adopt, maybe months, maybe years. I cannot believe the adoption comes so quickly. I think this is gonna be huge. What do you guys think?
- iLoveOncall 10mo ago
  Who wants a button that has indeterministic actions?
  - phacker007 10mo ago
    Calling it... Vibe clicking
  - seanhunter 10mo ago
    The popularity of slot machines suggests there is a market
  - isoprophlex 10mo ago
    [flagged]
  - stingraycharles 10mo ago
    Unless the MCP server itself has an LLM call inside of it (rare), the MCP server is pretty deterministic. It’s the AI that invokes it that’s actually indeterministic, but the user is already using that.
    - notpachet 10mo ago
      > pretty deterministic This is an oxymoron.
      - stingraycharles 10mo ago
        I meant “pretty” as in, using a search engine is pretty deterministic, any REST API is deterministic. MCP servers’ tools are literally just function calls. It’s the LLM MCP client that’s not deterministic, not the MCP server.
      - hobofan 10mo ago
        No it's not. In the real world, where it is (at least in our current state of overall programming language tooling, and the existence of physics) intractable to prove all eventualities and absence of side-effects of executed code, determinism is indeed a spectrum. If we want to be specific here, I would say the "pretty deterministic" is equal to "as deterministic as your typical non-LLM REST API call", which still spans a big range of determinism.
    - mercury24aug 10mo ago
      This is a very strict definition of MCP. An agent (with LLM call inside) can be an MCP. Event a UI component can be an MCP.
  - degamad 10mo ago
    > button that has indeterministic actions google.com (1998-present) [I'm feeling lucky]
  - mercury24aug 10mo ago
    AI fills in a form, and you want to adjust the form before clicking submit. How often do you have to adjust AI's answer vs accepting it as is
- jillesvangurp 10mo ago
  You are touching on an important point. Basically OpenAI and others provide a lot of poorly integrated tools and components. You can build nice things with those but you have to deal with a lot of issues and it's a non trivial amount of work that even they aren't doing apparently. Even such a simple thing as triggering an OAuth signin to get access to models is not part of SDKs. Most developer tools require configuring API keys in some file instead. No normal user is ever going to do that,. Things like ChatGPT are remarkably limited from a UX/UI point of view. The product can do amazing things but the UI is nothing special. The mac version currently has a bug where option+shift+1 opens a chat window but doesn't give it focus. When I do that from vs code it adds the editor window. But it's completely blind to any browser tab on which I do that. I'm sure there are good reasons for all that. But it strikes me a bit as a work in progress that a good product owner would spot. With apps some of the more powerful capabilities (llms driving UIs directly, doing things in agentic loops, tool and API usage) are going to require much deeper integrations than are currently there. We get hints of what is possible and nice technology demos. But it's still hard to build more complicated workflows around this. Unless you build your own applications. We've been staring at this from the point of view of automating some highly tedious stuff that we currently do in our company manually. For example, working with chat GPT seems to involve a lot of copy paste and manually doing things that it can't really do by itself. Even something as simple as working on a document it will do alright work on the text but then make a complete mess of the formatting. I spend an hour a few days ago iterating on a document where I was basically just fixing bullets and headers. Most alternatives I've tried aren't any better at this. None of this seems particularly hard; it's just a lot of integration work that just hasn't happened yet. We have a bunch of lego bricks, not a lot of fully mature solutions. MCP isn't a full solution, it's a pretty lego brick. Mostly even OpenAI and Anthropic aren't getting around to doing much more than simplistic technology demos with their own stuff. IMHO their product teams are a lot less remarkable than their AI teams.
r-u-serious 10mo ago
[flagged]
emilsedgh 10mo ago
I dont think people realize how important this is. If one of the vendors manages to get their protocol to become the target platform (eg oai and app sdk), that is essentially their vendor lock in to become the next iOS/Android. Private API’s or EEE strategies are gonna be something to keep an eye for and i wish regulators would step in to prevent them before its too late.
- CuriouslyC 10mo ago
  This is so backwards it's scary. Having a chatbot that drives websites inside of it is such an attempted monopolist play. Having a system agent that can interact with apps via API without being connected to the app is the pattern that's both elegant and preserves freedom.
  - yunwal 10mo ago
    I don't see how this is a step down from existing web applications. Should companies building web applications not be opinionated about their user interfaces? When I look at Notion, I should just get any view of the data inside it, regardless of whether it's the same view as my coworker gets? How is this preferable? > Having a system agent that can interact with apps via API without being connected to the app is the pattern that's both elegant and preserves freedom Does this prevent anyone from doing that?
- hobofan 10mo ago
  How is it any better if instead of _one_ vendor, _two_ vendors push an immature version of a standards extension that mainly caters to their needs and give it the official stamp of approval under the MCP umbrella?
qwertox 10mo ago
While they're at it, they might as well check if their answers end with a yes/no question, and, if so, offer a "yes" button so that i can answer yes with a single click. > If you want a focused comparison next - for example, benchmarks on coding/math, token-cost examples for a typical session, or API usage differences - I can produce a compact table with sources and numbers. --> can be answered with yes, so please add a yes button. A no button is not needed.
brazukadev 10mo ago
Original title: MCP Apps: Extending servers with interactive user interfaces The post title is quite editorialized.
- stingraycharles 10mo ago
  Correct, the title should be changed.
felixrieseberg 10mo ago
Disclosure: I work at Anthropic, have worked on MCP I also think this is pretty big. I think a problem we collectively have right now is that getting MCP closer to real user flows is pretty hard and requires a lot of handholding. Ideally, most users of MCP wouldn't even know that MCP is a thing - the same way your average user of the web has no idea about DNS/HTTP/WebSockets. They just know that the browser helps them look at puppy pictures, connect with friends, or get some work done. I think this is a meaningful step in the direction of getting more people who'll never know or care about MCP to get value out of MCP.
- iLoveOncall 10mo ago
  I wonder how long it'll take you to figure out that you're trying to reinvent deterministic APIs.
  - stingraycharles 10mo ago
    What is indeterministic about MCP servers? Most of them follow fairly simple rules, eg an MCP server to interact with Slack gives pretty deterministic responses to requests. Or are you confusing the LLM / MCP client invoking the tools being non-deterministic?
  - neoden 10mo ago
    MCP is already deterministic. What's huge about it is that it has automatic API discovery and integration built-in. It's a bit rough yet but I think we will only see how it's getting improved more and more.
    - degamad 10mo ago
      > automatic API discovery and integration So, WSDL?
      - neoden 10mo ago
        no, thank you
oulipo2 10mo ago
I'm not sure I get why we need something specific like MCP-UI? why wouldn't "just another tool" do exactly the same? Eg you present a "display-graph-chart" tool as a MCP tool, and the agent calls it, it doesn't need to adhere to any protocol except the basic existing MCP protocol, and the UI that's used to interact with the agent would know the best presentation (show it as an embedded HTML graph if in a web ui, show it as a ascii chart if in a terminal, etc)? Is the idea just to standardize the "output format" of the tool so that any agent UI could display stuff in the same way? so that one tool could work with any agent display?
mindwok 10mo ago
It'll be interesting to see how this goes, but my first impression is that it's actually not where we want to go. One of the cool things about MCP (or even just tool calling) is that the LLM on top of a tool provides a highly flexible and dynamic interface to traditionally static tools. I love being able to type "make an iptables rule that opens 443" instead of having to dig out the man page and remember how to do that. IMO the next natural extension of this is giving the LLM more capability to generate user interfaces so I can interact with stuff exactly bespoke to my task. This on the other hand seems the other way round, it's like bolting a static interface onto the LLM, which could defeat the purpose of the LLM interface layer in the first place right?
- ivape 10mo ago
  I personally don’t see why developers should just add tons of functionality to any model for free like this. Some of these MCPs are pretty good, and I was a little shocked how much functionality developers released for free to drop into something like Claude. Either developers are stupid or there really is no market yet.
  - kkarpkkarp 10mo ago
    > for free like this for free: not. but I'm certain the race has just begun: big service providers and online retailers are currently implementing widgets enabling the purchase of their services and goods directly within the ChatGPT or Claude chat windows.
- vidarh 10mo ago
  MCP has already drastically lost utility already thanks to skills - for most things it is easier to just hand the model a CLI that it can run. I'd imagine the same thing will happen here: It will prove more flexible to not push the model (and user) towards a UI that may not match what the user is trying to accomplish. To me this seems like something I categorically don't want unless it is purely advisory.
  - prescriptivist 10mo ago
risyachka 10mo ago
Am I missing something or is this essentially same as GPT Apps that have been introduced a while ago and have been discussed 10000 times.
- Maxious 10mo ago
  Turns the concept of GPT Apps into an open standard rather than something ChatGPT only.
noodletheworld 10mo ago
An, the dream, a cross platform App Store you can install apps into any client application that supports MCP, but is open, free and agentic. It’s basically a “web App Store” and we side step the existing app stores (and their content guidelines, security restrictions and billing requirements) because it’s all done via a mega app (the MCP client). How could it go wrong? If only someone had done this before, we wouldnt be stuck in Apples, etc’s walled gardens… Seriously though; honest question: this is literally circumventing platform requirements to use the platform app stores. How do you imagine this is going to be allowed? Is ChatGPT really big enough they can pull the “we’re gonna do it, watcha gonna do?” to Apple? Who’s going to curate this app store so non technical users (the explicitly stated audience) can discover these MCP apps? It feels like MCP itself; half baked. Overly ambitious. “We’ll figure the details out later”
- ivape 10mo ago
  The apps are LLM agnostic, so all MCP apps will be portable. Economically, this means developers don’t have convince users to pay $20 a month, these users are already paying that. Devs just have to convince users to buy the app on the platform. I don’t see this being the future state. We’d be talking about a world where any and all apps exist inside of fucking ChatGPT and that just sounds ridiculous.
ilaksh 10mo ago
I skimmed over this, but did I see a reference sandbox implementation? And then basically the chat UI interacts with that with postMessage (and receiving) and forwards tool calls to the MCP server. Does it also forward tool calls the MCP server doesn't handle to the host backend? What I am imagining is something like a meta UI tool call that just creates a menu. The whole MCP server's purpose might be to add this menu creation capability to the chat user interface. But what you are selecting from isn't known ahead of time, it's the input to the UI. When they select something I assume it would output a tool call like menuItemSelected('option B'). I suppose if you want your server to do anything specific with this then you would have to handle that in the particular server. But I guess you could also just have a tool call that just sends the inputs to the agent. This could make for what is a very slow to respond but extremely flexible overall UX. I guess this is not the intended use, but suppose you give your agent generic MCP UI tools for showing any menu, showing any data table, showing a form, etc. So the inputSchemas would be somehow (if this is possible) quite loosely defined. I guess the purpose is probably more about not having to go through the LLM rather than giving it the ability to dynamically put up UI elements that it has to react to individual interactions with. But maybe one of the inputs to the dataTable are the query parameters for its data, and the table has a refresh button. Maybe another input is the URI for the details form MCP UI that slides over when you click a row. Maybe there is an MCP UI for Layout what allows you to embed other MCP UIs in a specific structure. This might not make sense, but I am wondering if I can use MCP Apps as an alternative to always building custom MindRoot plugins (my Python/web components agentic app framework) to provide unique web pages and UI for each client's agentic application. I think I may have gotten the MCP Apps and MCP UI a bit conflated here so I probably need to read it again.
WillAdams 10mo ago
How reliable are the processes which these things run? I'm processing thousands of files using Copilot, and even 20 at a time, it usually skips a couple, and sometimes, when skipping, it merges the data from one file to the next, not applying anything to the second file, other times it completely applies the data parsed from one file to the second --- not a big deal since I'm reviewing each operation manually, but the only reason the error rate is acceptable is the files are so inconsistent that normal techniques weren't working. Is there an equivalent to "double-keying" where two different LLMs process the same input and it only moves forward if both match perfectly?
- seunosewa 10mo ago
  You should probably ask the AI to write a script to do the task. Any procedure that needs to be perfect should be done by writing deterministic code.
  - WillAdams 10mo ago
    The task is renaming scans of checks (with the barcode/bank account info obscured by a pen) --- the checks are of varying sizes, placement is not exact, the placement and formatting of the information on the check is essentially random, and many of them are (poorly) handwritten). The LLM is working well enough for my needs (and I'm using a locked-down computer which installing/running development environments/scripts on is awkward), and it's a marked improvement over the previous technique of opening 50 files at a time, noting the Invoice ID, closing the file, typing the Invoice ID as a name, then quitting Adobe Acrobat and re-launching it for the next 50 (if that was not done, eventually Acrobat would reach a state where it would close a file and despite the name having been typed, not save it), then using a .bat file made using concatenation in an Excel column. It would be nice if it were perfect, but each check has to be manually entered, and the filename updated to match the entry by hand.
- Yodan2025 10mo ago
  test how much data from a file they actually see.. its not unlimited// build a deterministic output ie. 2 of 5 chunks received, send chunk 3
notpachet 10mo ago
Can we edit the submission title to match what's in the actual article? Not just because I'm annoyed at how transparently Gen Z the HN title is...
CuriouslyC 10mo ago
IMO this is not where we want to go. The future is you have a system agent that interact with all your apps via API, and websites are real-time so you can see what your agent is doing as you do it it. We don't need more rigging for this future, just better API support. Trying to create custom agent APIs to embed apps in chat is a very "monopolist frontier lab" thing to try and do.
meander_water 10mo ago
We already have AG-UI [0], which has been implemented by frameworks like Microsoft agent framework, pydantic AI and llamaindex. I guess they'll just have to duplicate functionality. Sigh. [0] https://docs.ag-ui.com/introduction https://docs.ag-ui.com/introduction
- Maxious 10mo ago
  We had AG-UI. I'd say CopilotKit and AssistantUI (YC W25) are now Sherlocked
  - autogn0me 10mo ago
    ?
- swiftlyTyped 10mo ago
  AG-UI is compatible with both MCP-UI and other declarative UI specs. AG-UI is built to support agentic behavior in your application, more similar to the Vercel AI SDK but horizontal and standardized. MCP-UI helps external apps and APIs pass UI to applications, really well suited for use cases like Shopify stores inside of ChatGPT.
hobofan 10mo ago
I am a pretty big proponent of MCP, and I think this at least for now is not a move in a good direction. The whole surface of the MCP specification is already pretty big, and barely any server implements anything beyond the core parts. With elicitation there was already a lightweight version of this in place in the standard, and I'm not sure I've ever encountered a server or client implementation of it in the wild, and elicitation is an order of magnitude simpler to integrate on a conceptional level. I fear that this has a significant risk of splintering the MCP ecosystem further (it's already pretty strained due to the transport protocol iterations), and there isn't really a reason to create a official extension (yet), that may worst case also require multiple iterations to get things right.
- somnium_sn 10mo ago
  All it means that there is a common place and a recommendation that if you care as a client implementor (e.g. postman, chatgpt and others do), there is a spot to look for a generally accepted way of how to do that instead of increasing amount of proprietary extensions on top of MCP.
  - hobofan 10mo ago
    > there is a spot to look for a generally accepted way of how to do that I think MCP-UI in it's current state can fill that role very well, and that's not the only lens with which to view a SEP like this. From what I can tell the main thing that this SEP does is put the official blessing of the MCP project on the existing underlying protocol that MCP-UI is already using. I think the better way would be to let MCP-UI and competing implementations cook for a little bit longer, rather than trying to get an officially sanctioned extension out the door and then iterate on that, which will cause a lot more churn. For a non-trivial feature like this, I would expect an SEP that highlights more alternative usage scenarios and potentially operates on a more technology agonistic layer (e.g. it's very JS+iframe bound, so what about mobile or terminal UIs?), similar to the main MCP spec. Especially given the backdrop of the main MCP specification, which feels much more well-rounded and throughly considered (though in a few areas still incomplete), this SEP does not seem to meet the same bar. Reading that from the perspective of someone that builds a LLM Chat UI[0] (and aims to be able to maintain that long-term) that heavily builds on MCP as an interoperability concept, reading what is proposed here and seeing how prescriptive it is in many aspects does not spark a lot of joy. [0]: https://erato.chat https://erato.chat --- EDIT: From what I can tell I'm replying to one of the co-creators of MCP. So let me just ask quite directly: Do you think that the risk of proprietary sprawl in terms of MCP-UI alternatives is currently greater than prematurely standardizing a potentially incomplete version?
poisonborz 10mo ago
My fear is that even for consumer apps, MCP (or successor) will outgrow UIs, becoming the only way to interact with an app or certain feature - placing machines wholly in the center instead of humans. Human software should retain the understandability and atomicity of each step taken.
michaelbuckbee 10mo ago
In my current personal development workflow with Claude Code, I've switched entirely to using CLI tools and scripts over MCP as the experience is much more deterministic and flexible. A great example is Github, it's a significantly better dev experience having CC call out to the gh cli for actions than trying to invoke the MCP.
- bradgessler 10mo ago
  I built https://terminalwire.com https://terminalwire.com to make it easier for more web applications to ship CLIs like gh. Are there any web services like GH that you use in your workflow that don’t have decent AI integration that would benefit from a CLI interface?
_heimdall 10mo ago
If only we as an industry hadn't abandoned REST APIs none of this would be necessary. We've known for decades that its useful for APIs to be self documented and for responses to use schemas to define the shape of the data. XML can be verbose and I understand why people preferred JSON for ease use. Had we stuck with REST for the last 20 years we'd be way ahead on that front, though, both in syntax and tooling.
- hobofan 10mo ago
  > Had we stuck with REST for the last 20 years we'd be way ahead on that front We are where we are because there (sadly) hasn't been a reasonable business case to advance REST API documentation beyond the point of badly-documented OpenAPI schemas where the main utility is in generating type-safe API wrappers across different programming languages. With MCP, there is at least a name to a new movement to build self-describing APIs, as with the advent of LLMs there is now enough of a utility for it. All other pushes into that direction have died out ~10 years ago.
  - _heimdall 10mo ago
    Correct me if I'm wrong, but I thought OpenAPI was itself an attempt to wedge REST concepts back on top of mostly RPC-based APIs. I.e. add documentation and a standard set of schemas on top of JSON APIs (mostly). I do think the problem is from business concerns, though, and are a clear predictor that MCP will fail. Coming out of the dotcom bubble those left standing wanted to build moats and walls, not APIs that any third party could easily discover and use. The need for REST only shows up when a new player makes a move to effectively gobble up the role of being the gate keeper to the internet. With scale other companies will follow, but begrudgingly and only for a short while.
    - wild_egg 10mo ago
      Sadly not. One of the constraints of REST is that the API be completely self-descriptive. If you need out-of-band information like an API spec, then it's basically not RESTful by definition. I'm using a REST API to read your comment and submit my response — I didn't need to reference external HN API docs. The interface here is fully self-describing.
baq 10mo ago
What’s the difference between an MCP server and a command line executable (which curl is also one)? A good ——help or openapi spec…?
- brazukadev 10mo ago
  MCP defines other useful things like Resources, Elicitation, Sampling, prompts which are model/agent-specific, there is nothing in openai or a "good --help" that could match that. If you don't see this as useful, that is ok, but it is not the same as a command line executable.
- cube2222 10mo ago
  vs executable - don’t need a full shell environment to run it vs openapi - there’s some more advanced agent-specific concepts in MCP, but primarily, I would say, it’s convention and optimizing for the client. Existing openapi specs will often have not great descriptions, or be a huge mess, or just be huge. Making an MCP server requires you to rethink the UX and tools to be optimized for the access patterns of an agent, and also makes you test it with them. That said, Claude Skills[0] is something more in the vein of cli with —help (really, with a markdown guide), embracing what is already there with a bit of instructions, as opposed to building from scratch. My personal opinion, having built multiple MCP servers, is that long-term they will not be the primary approach to tools, and that skills for instance are a better approach for most use-cases. But they do have their use-cases. [0]: https://www.claude.com/blog/skills https://www.claude.com/blog/skills
  - debugnik 10mo ago
    You don't need a shell to run executables either.
UltraSane 10mo ago
Hasn't even Anthropic admitted that MCP is very wasteful of context? Having the LLM write code to call and API can use 98% less tokens. https://www.anthropic.com/engineering/code-execution-with-mcp https://www.anthropic.com/engineering/code-execution-with-mc... The agent discovers tools by exploring the filesystem: listing the ./servers/ directory to find available servers (like google-drive and salesforce), then reading the specific tool files it needs (like getDocument.ts and updateRecord.ts) to understand each tool's interface. This lets the agent load only the definitions it needs for the current task. This reduces the token usage from 150,000 tokens to 2,000 tokens—a time and cost saving of 98.7%.
- hobofan 10mo ago
  The article you link (and general movements in that area, like e.g. discussed here[0]) don't advocate for abandoning MCP, just that masquerading MCP usage as code usage makes it more efficient. In that system MCP still provides a valuable role to act as a tool discovery protocol, a role that would have to be filled one way or another unless you are building a system with a set of tools that is known ahead of time. [0]: https://news.ycombinator.com/item?id=45917182 https://news.ycombinator.com/item?id=45917182
  - esafak 10mo ago
    In that case discovery could be served through `ls` or AGENTS.md, right? So when should you really use MCP?
    - hobofan 10mo ago
      It sounds like you are viewing MCP servers through a narrow lens of local coding agents. I'm mostly working with MCP servers in the context of enterprise/organizational usage for connecting internal data sources and workflows/internal APIs through a standardized interface. There is no equivalent of a "ls or AGENTS.md" there, as there is no file system and no shell in those contexts.
      - 10mo ago
theturtletalks 10mo ago
MCP-UI is a game changer for conversational commerce! We’re building a decentralized marketplace using MCP-UI and our own Shopify alternative[0]. 0. https://marketplace.openship.org https://marketplace.openship.org
jimmydoe 10mo ago
2010 Facebook apps 2015 WeChat mini program ... 2025 MCP-UI I'm tired.
_pdp_ 10mo ago
This is so redundant it is beyond reason. Given LLMs can generate code complex frontend code, why is so difficult for Antropic / OpenAI to prompt their chat applications to create UI on the fly that matches 100% their Chat applications? I know this is possible because this is how we do it. The LLM generates some text that we know how to interpret and we render it on the screen. Besides, this is exactly how their canvas thing works (both chtgpt and claude) when rendering documents on the side.
- _pdp_ 10mo ago
  Also, this is how GitHub Copilot works when rendering UI to preview draft tickets. It is simply a markdown fenced codeblock with some special properties in the language definition. Not only this approach is more specific to the application where the UI is supposed to render but it also opens the door for the user to customise how the UI should work by adding their own prompts. The approach that OpenAI has taken is not better - it is simply a mechanism to create some sort of app store - something they have attempted to do many times in the past as well.
gessha 10mo ago
Meta note: I really detest authors using cryptobro terminology “A dropped” and “B is huge” for anything technical. It immediately smells of script kiddies or their latest reincarnation.
- _pdp_ 10mo ago
  Well the cryptobros moved into AI so not surprising. I know because we are getting 3-4 spam messages per day on our discord server from various developers with previous experience in crypto now looking for opportunities in the agentic AI development space.
mbreese 10mo ago
I don’t get it. I like MCP as an interface in general, but I don’t understand the use-case they present. For those of you here who like this idea, what is the killer use case? To me, this looks less like UI interactions and more like the MCP equivalent of maintaining state. You start your program and “click” buttons until you get the desired result, maintaining a constant state between interactions. Isn’t that currently possible if you passed through something like a session-id back to the LLM? Am I missing something? I’m struggling to see what a UI makes possible that the current workflow does not. I also generally see/use MCP in terms of remote access to programs through servers. Perhaps that’s where I’m getting lost. Is this exclusively something for local MCP?
- kkarpkkarp 10mo ago
  > For those of you here who like this idea, what is the killer use case? # 1 - Hey claude, recommend me next book I could read - sure, what about '1984'? Here is a button to send it directly to your kindle, it will be $4,99. # 2 - I am looking for the hotel for two in Viena this weekend - here are some offers and still available (displays grid view generated by mcp ui, handled by booking.com, each item has a button to "book now" directly)
  - mbreese 10mo ago
    Thank you for this. So, basically -- it's a method for the MCP Server to display a UI element to the user allowing the user to perform some kind of action. Current, this UI will be an HTML iframe. I think I got confused by their barchart example. I thought this would have been just as easily supported by the MCP server sending back a PNG/PDF of a barchart for the main interface to display (I also generally think of barcharts as static content). But, the idea of adding specific user interaction elements (buttons) helps to make the concept more clear to me.
- beders 10mo ago
  This is the first wave of a new generation of Apps which has the potential to replace/enhance the majority of e-commerce websites. I wouldn't underestimate it - it's the hammer can break up the information silos we've built up around websites/apps. Why prompt Gertrude(tm) on Ramazon for a specific thing you need, if you can ask ChatGPT to find you said thing along with UIs to purchase it across all e-commerce platforms that agree to play in this market?
no_circuit 10mo ago
Yes, it is huge to spread the work out on embedded UIs in chat interfaces. But I think the design direction is going, is exactly the same direction of how Google Assistant, Amazon Alexa, or any of the other assistants work, ifkyk. The MCP community is just reinventing, but yes, improving, what we've done before in the previous generation: Microsoft Bot Framework, Speaktoit aka Google Dialogflow, Siri App Shortcuts / Spotlight. And interactive UIs in chats go back at least 20 years, maybe not with an AI agent attached... The next thing that will be reinvented is the memory/tool combination, aka a world model.
pragmatic 10mo ago
So we just reinvented web pages from first principles? I think I have to be missing what is huge here?
luigipederzani 10mo ago
Building MCP Apps (MCP servers with Apps SDK support) is pretty painful right now. You need to: 1. Spin up a server that returns UI components. 2. Hand-write a bunch of JSON schemas + tool wiring So we open-sourced a high-level MCP Server SDK that basically lets you have both the MCP server and React components in the same place: - Every React component you put in your resources/ folder is automatically built and exposed as an MCP resource + tools. No extra registration boilerplate. - We added a useWidget hook that takes the tool args and maps them directly into your component props, so the agent effectively “knows” what data the widget needs to render. You focus on UI + logic, the SDK handles the plumbing Docs for that flow here: https://docs.mcp-use.com/typescript/server/creating-apps-sdk-server https://docs.mcp-use.com/typescript/server/creating-apps-sdk... We also shipped an MCP Inspector to make the dev loop much less painful: you can connect your MCP server, test UI components from tools (with auto-refresh), and debug how it behaves with ChatGPT/agents as you iterate. https://docs.mcp-use.com/inspector/debugging-chatgpt-apps https://docs.mcp-use.com/inspector/debugging-chatgpt-apps Both the SDK and the Inspector are open-source, and any contributions are very welcome :) Those are the repos: - SDK: https://github.com/mcp-use/mcp-use https://github.com/mcp-use/mcp-use - Inspector: https://github.com/mcp-use/mcp-use/tree/main/libraries/typescript/packages/inspector https://github.com/mcp-use/mcp-use/tree/main/libraries/types...
adidoit 10mo ago
It's very interesting of course at a natural move for aggregation. I'd love to see Stratechery / Ben Thompson's take on this. From my perspective the challenges for vendors and SaaS providers are [1] discovery [2] monetization [3] disintermediation I think it's less of a concern if you're Shopify or those large companies that have existing brand moats. But if you're a startup, I don't think MCP as a channel is a clear-cut decision. Maybe you can get distribution but monetization is not defined. Also I'm sure the model providers will capture usage data and could easily disintermediate you , especially if your startup is just a narrow set of prompts and a UX over a specific workflow. The Reforge guys have been talking about a channel shift and this being it but until incentives are clear I'm not sure this is it yet. Maybe an evolution of this. I'm building an AI coach for job seekers / early stage professionals (Socratify) and while I'd love more distribution from MCP UI integration I think at this point risk is higher than reward...
greatgib 10mo ago
When you think about that, without AI, simple automation could do most of what we would need if app and webapp providers would have been to provide interface. Were instead the big fight was to prevent scraping and to get your info in any other way than being forced to use the crappy app. Like for banking.
- woleium 10mo ago
  many banks have api access now, but maybe only for business accounts?
  - tyfon 10mo ago
    In Europe we have the PSD2 open banking [1] directive which essentially gives developers a standard api access to banking operations on behalf of a user. It is a requirement for banks to implement this and the FSA will be on your neck if you are not compliant with the standard. [1] https://finance.ec.europa.eu/regulation-and-supervision/financial-services-legislation/implementing-and-delegated-acts/payment-services-directive_en https://finance.ec.europa.eu/regulation-and-supervision/fina...
    - debugnik 10mo ago
      To access that API you need a license as an authorised third-party provider (TPP), don't you? So in practice it is only for businesses capable of pushing through the bureaucracy.
doug_durham 10mo ago
Sounds interesting, but I'm pretty unimpressed with "specification first" approaches. Build a tool and release it. If it resonates the let that be the basis for future standards.
hamasho 10mo ago
One thing I like about the current AI craze is that several services start to provide user-oriented services again, like 90s and 00s. Search engine for AI returning only relevant results (no ads and promotions), online stores showing only relevant items, news articles in non-clickbait, clear and concise style. I'm not confident the current AI craze will be net positive for humanity. But one possible good outcome could be that many people prefer simple chat UI to interact with services, most companies have to adopt them and are forced to provide simple, straight, no-nonsense content instead of what they want to sell, while LLMs are just commodity so unnamed Chinese companies can provide models as good as the one from the most VC-funded company so they can't enshittify the UX.
samchon 10mo ago
Amazing

192 points by mercury24aug 10mo ago

Looks like OpenAI, Anthropic, and the MCP-UI team actually worked together on a common standard for MCP Apps: https://blog.modelcontextprotocol.io/posts/2025-11-21-mcp-apps/ https://blog.modelcontextprotocol.io/posts/2025-11-21-mcp-ap... Honestly, I think the biggest friction for MCP adoption has been how un-userfriendly it is. It’s great for devs, but not the average users. Users don't always want to chat, sometimes they just want to click a button or adjust a slider. This feels like the answer to that problem. Full disclosure, I'm partial here because of our work at https://usefractal.dev https://usefractal.dev. We were early adopters when MCP first came out, but we always felt like something was missing. We kept wishing for a UI layer on top, and everyone says it's gonna take forever for the industry to adopt, maybe months, maybe years. I cannot believe the adoption comes so quickly. I think this is gonna be huge. What do you guys think?

iLoveOncall 10mo ago
Who wants a button that has indeterministic actions?
- phacker007 10mo ago
  Calling it... Vibe clicking
- seanhunter 10mo ago
  The popularity of slot machines suggests there is a market
- isoprophlex 10mo ago
  [flagged]
- stingraycharles 10mo ago
  Unless the MCP server itself has an LLM call inside of it (rare), the MCP server is pretty deterministic. It’s the AI that invokes it that’s actually indeterministic, but the user is already using that.
  - notpachet 10mo ago
    > pretty deterministic This is an oxymoron.
    - stingraycharles 10mo ago
      I meant “pretty” as in, using a search engine is pretty deterministic, any REST API is deterministic. MCP servers’ tools are literally just function calls. It’s the LLM MCP client that’s not deterministic, not the MCP server.
    - hobofan 10mo ago
      No it's not. In the real world, where it is (at least in our current state of overall programming language tooling, and the existence of physics) intractable to prove all eventualities and absence of side-effects of executed code, determinism is indeed a spectrum. If we want to be specific here, I would say the "pretty deterministic" is equal to "as deterministic as your typical non-LLM REST API call", which still spans a big range of determinism.
  - mercury24aug 10mo ago
    This is a very strict definition of MCP. An agent (with LLM call inside) can be an MCP. Event a UI component can be an MCP.
- degamad 10mo ago
  > button that has indeterministic actions google.com (1998-present) [I'm feeling lucky]
- mercury24aug 10mo ago
  AI fills in a form, and you want to adjust the form before clicking submit. How often do you have to adjust AI's answer vs accepting it as is
jillesvangurp 10mo ago
You are touching on an important point. Basically OpenAI and others provide a lot of poorly integrated tools and components. You can build nice things with those but you have to deal with a lot of issues and it's a non trivial amount of work that even they aren't doing apparently. Even such a simple thing as triggering an OAuth signin to get access to models is not part of SDKs. Most developer tools require configuring API keys in some file instead. No normal user is ever going to do that,. Things like ChatGPT are remarkably limited from a UX/UI point of view. The product can do amazing things but the UI is nothing special. The mac version currently has a bug where option+shift+1 opens a chat window but doesn't give it focus. When I do that from vs code it adds the editor window. But it's completely blind to any browser tab on which I do that. I'm sure there are good reasons for all that. But it strikes me a bit as a work in progress that a good product owner would spot. With apps some of the more powerful capabilities (llms driving UIs directly, doing things in agentic loops, tool and API usage) are going to require much deeper integrations than are currently there. We get hints of what is possible and nice technology demos. But it's still hard to build more complicated workflows around this. Unless you build your own applications. We've been staring at this from the point of view of automating some highly tedious stuff that we currently do in our company manually. For example, working with chat GPT seems to involve a lot of copy paste and manually doing things that it can't really do by itself. Even something as simple as working on a document it will do alright work on the text but then make a complete mess of the formatting. I spend an hour a few days ago iterating on a document where I was basically just fixing bullets and headers. Most alternatives I've tried aren't any better at this. None of this seems particularly hard; it's just a lot of integration work that just hasn't happened yet. We have a bunch of lego bricks, not a lot of fully mature solutions. MCP isn't a full solution, it's a pretty lego brick. Mostly even OpenAI and Anthropic aren't getting around to doing much more than simplistic technology demos with their own stuff. IMHO their product teams are a lot less remarkable than their AI teams.

r-u-serious 10mo ago

[flagged]

emilsedgh 10mo ago

I dont think people realize how important this is. If one of the vendors manages to get their protocol to become the target platform (eg oai and app sdk), that is essentially their vendor lock in to become the next iOS/Android. Private API’s or EEE strategies are gonna be something to keep an eye for and i wish regulators would step in to prevent them before its too late.

CuriouslyC 10mo ago
This is so backwards it's scary. Having a chatbot that drives websites inside of it is such an attempted monopolist play. Having a system agent that can interact with apps via API without being connected to the app is the pattern that's both elegant and preserves freedom.
- yunwal 10mo ago
  I don't see how this is a step down from existing web applications. Should companies building web applications not be opinionated about their user interfaces? When I look at Notion, I should just get any view of the data inside it, regardless of whether it's the same view as my coworker gets? How is this preferable? > Having a system agent that can interact with apps via API without being connected to the app is the pattern that's both elegant and preserves freedom Does this prevent anyone from doing that?
hobofan 10mo ago
How is it any better if instead of _one_ vendor, _two_ vendors push an immature version of a standards extension that mainly caters to their needs and give it the official stamp of approval under the MCP umbrella?

qwertox 10mo ago

While they're at it, they might as well check if their answers end with a yes/no question, and, if so, offer a "yes" button so that i can answer yes with a single click. > If you want a focused comparison next - for example, benchmarks on coding/math, token-cost examples for a typical session, or API usage differences - I can produce a compact table with sources and numbers. --> can be answered with yes, so please add a yes button. A no button is not needed.

brazukadev 10mo ago

Original title: MCP Apps: Extending servers with interactive user interfaces The post title is quite editorialized.

stingraycharles 10mo ago
Correct, the title should be changed.

felixrieseberg 10mo ago

Disclosure: I work at Anthropic, have worked on MCP I also think this is pretty big. I think a problem we collectively have right now is that getting MCP closer to real user flows is pretty hard and requires a lot of handholding. Ideally, most users of MCP wouldn't even know that MCP is a thing - the same way your average user of the web has no idea about DNS/HTTP/WebSockets. They just know that the browser helps them look at puppy pictures, connect with friends, or get some work done. I think this is a meaningful step in the direction of getting more people who'll never know or care about MCP to get value out of MCP.

iLoveOncall 10mo ago
I wonder how long it'll take you to figure out that you're trying to reinvent deterministic APIs.
- stingraycharles 10mo ago
  What is indeterministic about MCP servers? Most of them follow fairly simple rules, eg an MCP server to interact with Slack gives pretty deterministic responses to requests. Or are you confusing the LLM / MCP client invoking the tools being non-deterministic?
- neoden 10mo ago
  MCP is already deterministic. What's huge about it is that it has automatic API discovery and integration built-in. It's a bit rough yet but I think we will only see how it's getting improved more and more.
  - degamad 10mo ago
    > automatic API discovery and integration So, WSDL?
    - neoden 10mo ago
      no, thank you

oulipo2 10mo ago

I'm not sure I get why we need something specific like MCP-UI? why wouldn't "just another tool" do exactly the same? Eg you present a "display-graph-chart" tool as a MCP tool, and the agent calls it, it doesn't need to adhere to any protocol except the basic existing MCP protocol, and the UI that's used to interact with the agent would know the best presentation (show it as an embedded HTML graph if in a web ui, show it as a ascii chart if in a terminal, etc)? Is the idea just to standardize the "output format" of the tool so that any agent UI could display stuff in the same way? so that one tool could work with any agent display?

mindwok 10mo ago

It'll be interesting to see how this goes, but my first impression is that it's actually not where we want to go. One of the cool things about MCP (or even just tool calling) is that the LLM on top of a tool provides a highly flexible and dynamic interface to traditionally static tools. I love being able to type "make an iptables rule that opens 443" instead of having to dig out the man page and remember how to do that. IMO the next natural extension of this is giving the LLM more capability to generate user interfaces so I can interact with stuff exactly bespoke to my task. This on the other hand seems the other way round, it's like bolting a static interface onto the LLM, which could defeat the purpose of the LLM interface layer in the first place right?

ivape 10mo ago
I personally don’t see why developers should just add tons of functionality to any model for free like this. Some of these MCPs are pretty good, and I was a little shocked how much functionality developers released for free to drop into something like Claude. Either developers are stupid or there really is no market yet.
- kkarpkkarp 10mo ago
  > for free like this for free: not. but I'm certain the race has just begun: big service providers and online retailers are currently implementing widgets enabling the purchase of their services and goods directly within the ChatGPT or Claude chat windows.
vidarh 10mo ago
MCP has already drastically lost utility already thanks to skills - for most things it is easier to just hand the model a CLI that it can run. I'd imagine the same thing will happen here: It will prove more flexible to not push the model (and user) towards a UI that may not match what the user is trying to accomplish. To me this seems like something I categorically don't want unless it is purely advisory.
- prescriptivist 10mo ago

risyachka 10mo ago

Am I missing something or is this essentially same as GPT Apps that have been introduced a while ago and have been discussed 10000 times.

Maxious 10mo ago
Turns the concept of GPT Apps into an open standard rather than something ChatGPT only.

noodletheworld 10mo ago

An, the dream, a cross platform App Store you can install apps into any client application that supports MCP, but is open, free and agentic. It’s basically a “web App Store” and we side step the existing app stores (and their content guidelines, security restrictions and billing requirements) because it’s all done via a mega app (the MCP client). How could it go wrong? If only someone had done this before, we wouldnt be stuck in Apples, etc’s walled gardens… Seriously though; honest question: this is literally circumventing platform requirements to use the platform app stores. How do you imagine this is going to be allowed? Is ChatGPT really big enough they can pull the “we’re gonna do it, watcha gonna do?” to Apple? Who’s going to curate this app store so non technical users (the explicitly stated audience) can discover these MCP apps? It feels like MCP itself; half baked. Overly ambitious. “We’ll figure the details out later”

ivape 10mo ago
The apps are LLM agnostic, so all MCP apps will be portable. Economically, this means developers don’t have convince users to pay $20 a month, these users are already paying that. Devs just have to convince users to buy the app on the platform. I don’t see this being the future state. We’d be talking about a world where any and all apps exist inside of fucking ChatGPT and that just sounds ridiculous.

ilaksh 10mo ago

I skimmed over this, but did I see a reference sandbox implementation? And then basically the chat UI interacts with that with postMessage (and receiving) and forwards tool calls to the MCP server. Does it also forward tool calls the MCP server doesn't handle to the host backend? What I am imagining is something like a meta UI tool call that just creates a menu. The whole MCP server's purpose might be to add this menu creation capability to the chat user interface. But what you are selecting from isn't known ahead of time, it's the input to the UI. When they select something I assume it would output a tool call like menuItemSelected('option B'). I suppose if you want your server to do anything specific with this then you would have to handle that in the particular server. But I guess you could also just have a tool call that just sends the inputs to the agent. This could make for what is a very slow to respond but extremely flexible overall UX. I guess this is not the intended use, but suppose you give your agent generic MCP UI tools for showing any menu, showing any data table, showing a form, etc. So the inputSchemas would be somehow (if this is possible) quite loosely defined. I guess the purpose is probably more about not having to go through the LLM rather than giving it the ability to dynamically put up UI elements that it has to react to individual interactions with. But maybe one of the inputs to the dataTable are the query parameters for its data, and the table has a refresh button. Maybe another input is the URI for the details form MCP UI that slides over when you click a row. Maybe there is an MCP UI for Layout what allows you to embed other MCP UIs in a specific structure. This might not make sense, but I am wondering if I can use MCP Apps as an alternative to always building custom MindRoot plugins (my Python/web components agentic app framework) to provide unique web pages and UI for each client's agentic application. I think I may have gotten the MCP Apps and MCP UI a bit conflated here so I probably need to read it again.

WillAdams 10mo ago

How reliable are the processes which these things run? I'm processing thousands of files using Copilot, and even 20 at a time, it usually skips a couple, and sometimes, when skipping, it merges the data from one file to the next, not applying anything to the second file, other times it completely applies the data parsed from one file to the second --- not a big deal since I'm reviewing each operation manually, but the only reason the error rate is acceptable is the files are so inconsistent that normal techniques weren't working. Is there an equivalent to "double-keying" where two different LLMs process the same input and it only moves forward if both match perfectly?

seunosewa 10mo ago
You should probably ask the AI to write a script to do the task. Any procedure that needs to be perfect should be done by writing deterministic code.
- WillAdams 10mo ago
  The task is renaming scans of checks (with the barcode/bank account info obscured by a pen) --- the checks are of varying sizes, placement is not exact, the placement and formatting of the information on the check is essentially random, and many of them are (poorly) handwritten). The LLM is working well enough for my needs (and I'm using a locked-down computer which installing/running development environments/scripts on is awkward), and it's a marked improvement over the previous technique of opening 50 files at a time, noting the Invoice ID, closing the file, typing the Invoice ID as a name, then quitting Adobe Acrobat and re-launching it for the next 50 (if that was not done, eventually Acrobat would reach a state where it would close a file and despite the name having been typed, not save it), then using a .bat file made using concatenation in an Excel column. It would be nice if it were perfect, but each check has to be manually entered, and the filename updated to match the entry by hand.
Yodan2025 10mo ago
test how much data from a file they actually see.. its not unlimited// build a deterministic output ie. 2 of 5 chunks received, send chunk 3

notpachet 10mo ago

Can we edit the submission title to match what's in the actual article? Not just because I'm annoyed at how transparently Gen Z the HN title is...

CuriouslyC 10mo ago

IMO this is not where we want to go. The future is you have a system agent that interact with all your apps via API, and websites are real-time so you can see what your agent is doing as you do it it. We don't need more rigging for this future, just better API support. Trying to create custom agent APIs to embed apps in chat is a very "monopolist frontier lab" thing to try and do.

meander_water 10mo ago

We already have AG-UI [0], which has been implemented by frameworks like Microsoft agent framework, pydantic AI and llamaindex. I guess they'll just have to duplicate functionality. Sigh. [0] https://docs.ag-ui.com/introduction https://docs.ag-ui.com/introduction

Maxious 10mo ago
We had AG-UI. I'd say CopilotKit and AssistantUI (YC W25) are now Sherlocked
- autogn0me 10mo ago
  ?
swiftlyTyped 10mo ago
AG-UI is compatible with both MCP-UI and other declarative UI specs. AG-UI is built to support agentic behavior in your application, more similar to the Vercel AI SDK but horizontal and standardized. MCP-UI helps external apps and APIs pass UI to applications, really well suited for use cases like Shopify stores inside of ChatGPT.

hobofan 10mo ago

I am a pretty big proponent of MCP, and I think this at least for now is not a move in a good direction. The whole surface of the MCP specification is already pretty big, and barely any server implements anything beyond the core parts. With elicitation there was already a lightweight version of this in place in the standard, and I'm not sure I've ever encountered a server or client implementation of it in the wild, and elicitation is an order of magnitude simpler to integrate on a conceptional level. I fear that this has a significant risk of splintering the MCP ecosystem further (it's already pretty strained due to the transport protocol iterations), and there isn't really a reason to create a official extension (yet), that may worst case also require multiple iterations to get things right.

somnium_sn 10mo ago
All it means that there is a common place and a recommendation that if you care as a client implementor (e.g. postman, chatgpt and others do), there is a spot to look for a generally accepted way of how to do that instead of increasing amount of proprietary extensions on top of MCP.
- hobofan 10mo ago
  > there is a spot to look for a generally accepted way of how to do that I think MCP-UI in it's current state can fill that role very well, and that's not the only lens with which to view a SEP like this. From what I can tell the main thing that this SEP does is put the official blessing of the MCP project on the existing underlying protocol that MCP-UI is already using. I think the better way would be to let MCP-UI and competing implementations cook for a little bit longer, rather than trying to get an officially sanctioned extension out the door and then iterate on that, which will cause a lot more churn. For a non-trivial feature like this, I would expect an SEP that highlights more alternative usage scenarios and potentially operates on a more technology agonistic layer (e.g. it's very JS+iframe bound, so what about mobile or terminal UIs?), similar to the main MCP spec. Especially given the backdrop of the main MCP specification, which feels much more well-rounded and throughly considered (though in a few areas still incomplete), this SEP does not seem to meet the same bar. Reading that from the perspective of someone that builds a LLM Chat UI[0] (and aims to be able to maintain that long-term) that heavily builds on MCP as an interoperability concept, reading what is proposed here and seeing how prescriptive it is in many aspects does not spark a lot of joy. [0]: https://erato.chat https://erato.chat --- EDIT: From what I can tell I'm replying to one of the co-creators of MCP. So let me just ask quite directly: Do you think that the risk of proprietary sprawl in terms of MCP-UI alternatives is currently greater than prematurely standardizing a potentially incomplete version?

poisonborz 10mo ago

My fear is that even for consumer apps, MCP (or successor) will outgrow UIs, becoming the only way to interact with an app or certain feature - placing machines wholly in the center instead of humans. Human software should retain the understandability and atomicity of each step taken.

michaelbuckbee 10mo ago

In my current personal development workflow with Claude Code, I've switched entirely to using CLI tools and scripts over MCP as the experience is much more deterministic and flexible. A great example is Github, it's a significantly better dev experience having CC call out to the gh cli for actions than trying to invoke the MCP.

bradgessler 10mo ago
I built https://terminalwire.com https://terminalwire.com to make it easier for more web applications to ship CLIs like gh. Are there any web services like GH that you use in your workflow that don’t have decent AI integration that would benefit from a CLI interface?

_heimdall 10mo ago

If only we as an industry hadn't abandoned REST APIs none of this would be necessary. We've known for decades that its useful for APIs to be self documented and for responses to use schemas to define the shape of the data. XML can be verbose and I understand why people preferred JSON for ease use. Had we stuck with REST for the last 20 years we'd be way ahead on that front, though, both in syntax and tooling.

hobofan 10mo ago
> Had we stuck with REST for the last 20 years we'd be way ahead on that front We are where we are because there (sadly) hasn't been a reasonable business case to advance REST API documentation beyond the point of badly-documented OpenAPI schemas where the main utility is in generating type-safe API wrappers across different programming languages. With MCP, there is at least a name to a new movement to build self-describing APIs, as with the advent of LLMs there is now enough of a utility for it. All other pushes into that direction have died out ~10 years ago.
- _heimdall 10mo ago
  Correct me if I'm wrong, but I thought OpenAPI was itself an attempt to wedge REST concepts back on top of mostly RPC-based APIs. I.e. add documentation and a standard set of schemas on top of JSON APIs (mostly). I do think the problem is from business concerns, though, and are a clear predictor that MCP will fail. Coming out of the dotcom bubble those left standing wanted to build moats and walls, not APIs that any third party could easily discover and use. The need for REST only shows up when a new player makes a move to effectively gobble up the role of being the gate keeper to the internet. With scale other companies will follow, but begrudgingly and only for a short while.
  - wild_egg 10mo ago
    Sadly not. One of the constraints of REST is that the API be completely self-descriptive. If you need out-of-band information like an API spec, then it's basically not RESTful by definition. I'm using a REST API to read your comment and submit my response — I didn't need to reference external HN API docs. The interface here is fully self-describing.

baq 10mo ago

What’s the difference between an MCP server and a command line executable (which curl is also one)? A good ——help or openapi spec…?

brazukadev 10mo ago
MCP defines other useful things like Resources, Elicitation, Sampling, prompts which are model/agent-specific, there is nothing in openai or a "good --help" that could match that. If you don't see this as useful, that is ok, but it is not the same as a command line executable.
cube2222 10mo ago
vs executable - don’t need a full shell environment to run it vs openapi - there’s some more advanced agent-specific concepts in MCP, but primarily, I would say, it’s convention and optimizing for the client. Existing openapi specs will often have not great descriptions, or be a huge mess, or just be huge. Making an MCP server requires you to rethink the UX and tools to be optimized for the access patterns of an agent, and also makes you test it with them. That said, Claude Skills[0] is something more in the vein of cli with —help (really, with a markdown guide), embracing what is already there with a bit of instructions, as opposed to building from scratch. My personal opinion, having built multiple MCP servers, is that long-term they will not be the primary approach to tools, and that skills for instance are a better approach for most use-cases. But they do have their use-cases. [0]: https://www.claude.com/blog/skills https://www.claude.com/blog/skills
- debugnik 10mo ago
  You don't need a shell to run executables either.

UltraSane 10mo ago

Hasn't even Anthropic admitted that MCP is very wasteful of context? Having the LLM write code to call and API can use 98% less tokens. https://www.anthropic.com/engineering/code-execution-with-mcp https://www.anthropic.com/engineering/code-execution-with-mc... The agent discovers tools by exploring the filesystem: listing the ./servers/ directory to find available servers (like google-drive and salesforce), then reading the specific tool files it needs (like getDocument.ts and updateRecord.ts) to understand each tool's interface. This lets the agent load only the definitions it needs for the current task. This reduces the token usage from 150,000 tokens to 2,000 tokens—a time and cost saving of 98.7%.

hobofan 10mo ago
The article you link (and general movements in that area, like e.g. discussed here[0]) don't advocate for abandoning MCP, just that masquerading MCP usage as code usage makes it more efficient. In that system MCP still provides a valuable role to act as a tool discovery protocol, a role that would have to be filled one way or another unless you are building a system with a set of tools that is known ahead of time. [0]: https://news.ycombinator.com/item?id=45917182 https://news.ycombinator.com/item?id=45917182
- esafak 10mo ago
  In that case discovery could be served through `ls` or AGENTS.md, right? So when should you really use MCP?
  - hobofan 10mo ago
    It sounds like you are viewing MCP servers through a narrow lens of local coding agents. I'm mostly working with MCP servers in the context of enterprise/organizational usage for connecting internal data sources and workflows/internal APIs through a standardized interface. There is no equivalent of a "ls or AGENTS.md" there, as there is no file system and no shell in those contexts.
    - 10mo ago

theturtletalks 10mo ago

MCP-UI is a game changer for conversational commerce! We’re building a decentralized marketplace using MCP-UI and our own Shopify alternative[0]. 0. https://marketplace.openship.org https://marketplace.openship.org

jimmydoe 10mo ago

2010 Facebook apps 2015 WeChat mini program ... 2025 MCP-UI I'm tired.

_pdp_ 10mo ago

This is so redundant it is beyond reason. Given LLMs can generate code complex frontend code, why is so difficult for Antropic / OpenAI to prompt their chat applications to create UI on the fly that matches 100% their Chat applications? I know this is possible because this is how we do it. The LLM generates some text that we know how to interpret and we render it on the screen. Besides, this is exactly how their canvas thing works (both chtgpt and claude) when rendering documents on the side.

_pdp_ 10mo ago
Also, this is how GitHub Copilot works when rendering UI to preview draft tickets. It is simply a markdown fenced codeblock with some special properties in the language definition. Not only this approach is more specific to the application where the UI is supposed to render but it also opens the door for the user to customise how the UI should work by adding their own prompts. The approach that OpenAI has taken is not better - it is simply a mechanism to create some sort of app store - something they have attempted to do many times in the past as well.

gessha 10mo ago

Meta note: I really detest authors using cryptobro terminology “A dropped” and “B is huge” for anything technical. It immediately smells of script kiddies or their latest reincarnation.

_pdp_ 10mo ago
Well the cryptobros moved into AI so not surprising. I know because we are getting 3-4 spam messages per day on our discord server from various developers with previous experience in crypto now looking for opportunities in the agentic AI development space.

mbreese 10mo ago

I don’t get it. I like MCP as an interface in general, but I don’t understand the use-case they present. For those of you here who like this idea, what is the killer use case? To me, this looks less like UI interactions and more like the MCP equivalent of maintaining state. You start your program and “click” buttons until you get the desired result, maintaining a constant state between interactions. Isn’t that currently possible if you passed through something like a session-id back to the LLM? Am I missing something? I’m struggling to see what a UI makes possible that the current workflow does not. I also generally see/use MCP in terms of remote access to programs through servers. Perhaps that’s where I’m getting lost. Is this exclusively something for local MCP?

kkarpkkarp 10mo ago
> For those of you here who like this idea, what is the killer use case? # 1 - Hey claude, recommend me next book I could read - sure, what about '1984'? Here is a button to send it directly to your kindle, it will be $4,99. # 2 - I am looking for the hotel for two in Viena this weekend - here are some offers and still available (displays grid view generated by mcp ui, handled by booking.com, each item has a button to "book now" directly)
- mbreese 10mo ago
  Thank you for this. So, basically -- it's a method for the MCP Server to display a UI element to the user allowing the user to perform some kind of action. Current, this UI will be an HTML iframe. I think I got confused by their barchart example. I thought this would have been just as easily supported by the MCP server sending back a PNG/PDF of a barchart for the main interface to display (I also generally think of barcharts as static content). But, the idea of adding specific user interaction elements (buttons) helps to make the concept more clear to me.
beders 10mo ago
This is the first wave of a new generation of Apps which has the potential to replace/enhance the majority of e-commerce websites. I wouldn't underestimate it - it's the hammer can break up the information silos we've built up around websites/apps. Why prompt Gertrude(tm) on Ramazon for a specific thing you need, if you can ask ChatGPT to find you said thing along with UIs to purchase it across all e-commerce platforms that agree to play in this market?

no_circuit 10mo ago

Yes, it is huge to spread the work out on embedded UIs in chat interfaces. But I think the design direction is going, is exactly the same direction of how Google Assistant, Amazon Alexa, or any of the other assistants work, ifkyk. The MCP community is just reinventing, but yes, improving, what we've done before in the previous generation: Microsoft Bot Framework, Speaktoit aka Google Dialogflow, Siri App Shortcuts / Spotlight. And interactive UIs in chats go back at least 20 years, maybe not with an AI agent attached... The next thing that will be reinvented is the memory/tool combination, aka a world model.

pragmatic 10mo ago

So we just reinvented web pages from first principles? I think I have to be missing what is huge here?

luigipederzani 10mo ago

Building MCP Apps (MCP servers with Apps SDK support) is pretty painful right now. You need to: 1. Spin up a server that returns UI components. 2. Hand-write a bunch of JSON schemas + tool wiring So we open-sourced a high-level MCP Server SDK that basically lets you have both the MCP server and React components in the same place: - Every React component you put in your resources/ folder is automatically built and exposed as an MCP resource + tools. No extra registration boilerplate. - We added a useWidget hook that takes the tool args and maps them directly into your component props, so the agent effectively “knows” what data the widget needs to render. You focus on UI + logic, the SDK handles the plumbing Docs for that flow here: https://docs.mcp-use.com/typescript/server/creating-apps-sdk-server https://docs.mcp-use.com/typescript/server/creating-apps-sdk... We also shipped an MCP Inspector to make the dev loop much less painful: you can connect your MCP server, test UI components from tools (with auto-refresh), and debug how it behaves with ChatGPT/agents as you iterate. https://docs.mcp-use.com/inspector/debugging-chatgpt-apps https://docs.mcp-use.com/inspector/debugging-chatgpt-apps Both the SDK and the Inspector are open-source, and any contributions are very welcome :) Those are the repos: - SDK: https://github.com/mcp-use/mcp-use https://github.com/mcp-use/mcp-use - Inspector: https://github.com/mcp-use/mcp-use/tree/main/libraries/typescript/packages/inspector https://github.com/mcp-use/mcp-use/tree/main/libraries/types...

adidoit 10mo ago

It's very interesting of course at a natural move for aggregation. I'd love to see Stratechery / Ben Thompson's take on this. From my perspective the challenges for vendors and SaaS providers are [1] discovery [2] monetization [3] disintermediation I think it's less of a concern if you're Shopify or those large companies that have existing brand moats. But if you're a startup, I don't think MCP as a channel is a clear-cut decision. Maybe you can get distribution but monetization is not defined. Also I'm sure the model providers will capture usage data and could easily disintermediate you , especially if your startup is just a narrow set of prompts and a UX over a specific workflow. The Reforge guys have been talking about a channel shift and this being it but until incentives are clear I'm not sure this is it yet. Maybe an evolution of this. I'm building an AI coach for job seekers / early stage professionals (Socratify) and while I'd love more distribution from MCP UI integration I think at this point risk is higher than reward...

greatgib 10mo ago

When you think about that, without AI, simple automation could do most of what we would need if app and webapp providers would have been to provide interface. Were instead the big fight was to prevent scraping and to get your info in any other way than being forced to use the crappy app. Like for banking.

woleium 10mo ago
many banks have api access now, but maybe only for business accounts?
- tyfon 10mo ago
  In Europe we have the PSD2 open banking [1] directive which essentially gives developers a standard api access to banking operations on behalf of a user. It is a requirement for banks to implement this and the FSA will be on your neck if you are not compliant with the standard. [1] https://finance.ec.europa.eu/regulation-and-supervision/financial-services-legislation/implementing-and-delegated-acts/payment-services-directive_en https://finance.ec.europa.eu/regulation-and-supervision/fina...
  - debugnik 10mo ago
    To access that API you need a license as an authorised third-party provider (TPP), don't you? So in practice it is only for businesses capable of pushing through the bureaucracy.

doug_durham 10mo ago

Sounds interesting, but I'm pretty unimpressed with "specification first" approaches. Build a tool and release it. If it resonates the let that be the basis for future standards.

hamasho 10mo ago

One thing I like about the current AI craze is that several services start to provide user-oriented services again, like 90s and 00s. Search engine for AI returning only relevant results (no ads and promotions), online stores showing only relevant items, news articles in non-clickbait, clear and concise style. I'm not confident the current AI craze will be net positive for humanity. But one possible good outcome could be that many people prefer simple chat UI to interact with services, most companies have to adopt them and are forced to provide simple, straight, no-nonsense content instead of what they want to sell, while LLMs are just commodity so unnamed Chinese companies can provide models as good as the one from the most VC-funded company so they can't enshittify the UX.

samchon 10mo ago

Amazing