The builder uses OpenAPI spec to define and implement the API. The backend aims to do what "normal" backend does: fulfills requests by executing business logic

The builder uses OpenAPI spec to define and implement the API. The backend aims to do what "normal" backend does: fulfills requests by executing business logic (written as functions, a form of DSL) and querying database. The very basic example of calculating average is just another type of "hello world" example. Separated frontend like a static html page can call API with an integer sequence and gets the average as the response. But your example of processing a form resonates, because most of the webapps are represented as some sort of forms. I will work with it to further develop the DSL. Thank you for the suggestion!