[Stoids]

I like the idea, especially the TS-like syntax around enums and union types. I've always preferred the SDL for GraphQL vs writing OpenAPI for similar reasons. Most APIs I've run into in my career would benefit from modeling their API responses as ADTs versus the usual approach of overloading 4 different union members into a giant spare object.

I echo the sentiment others have brought up, which is the trade-offs of a code-driven schema vs schema-driven code.

At work we use Pydantic and FastAPI to generate the OpenAPI contract, but there's some cruft and care needed around exposing those underlying Pydantic models through the API documentation. It's been easy to create schemas that have compatibility problems when run through other code generators. I know there are projects such as connexction[1] which attempt to inverse this, but I don't have much experience with it. In the GraphQL space it seems that code-first approaches are becoming more favored, though there's a different level of complexity needed to create a "typesafe" GraphQL server (eg. model mismatches between root query resolvers and field resolvers).

[1] https://github.com/spec-first/connexion