[Rabidgremlin]

100% agree with you... taking the time to do/go design first greatly improves the quality of the final API...

But as some comments below point out, an OpenAPI spec is a pain to create manually which is why TypeSpec from Microsoft is such a great tool. Lets you focus on the important bits of creating a solid API (model, consistency, best practices) in an easy to use DSL that spits out a fully documented OpenAPI spec to build against! see https://typespec.io/