It's this or writing openapi ymls... Even for people who know yml picking this up to define and write basic openapi definitions is much simpler than writing an openapi doc from hand, which is really painful
There is a framework in every language I've worked with that will generate the OpenAPI schema for you. That you have to sketch the API in a language is not necessarily "code-first", it's just a different language than yaml/json, (go,py,js) without the implementation, just write the same types in example
