I played with this using mustache, since Avro IDL can be materialized into Avro JSON IDL, and that is input into a template that spits out different outputs, including direct scaffolding to something like asyncio/python.

I personally vomit when I see all the REST verbs embedded in a Swagger interface specification. I prefer EDA over REST (aka ePoll at the OS level). To closely tied to REST for my taste.

As the world goes API first, I go domain model first, including Avro IDL, and perhaps a little OCL (aka DbC) "Aspects" (AOP wink).

I also want to capture relationships in a Semantic Graph model for RBE and AI integration.

If you've seen any tools that can take a UML class diagram, generate Avro -> generate REST and EDA based microservices to support async and sync naturally, in multiple language, transport, and persistence stacks -- well you be sure and speak up. :-)