While Swagger might not be perfect (some pain points are addressed with OpenAPI v3) it works IMHO pretty well for us (Zalando) and myself doing API first:

* use a decent editor to write the YAML e.g. https://github.com/zalando/intellij-swagger * do not write any boilerplate code and do not generate code (if that's possible in your env), e.g. by using https://github.com/zalando/connexion (Python API-first) * follow best practices and guidelines to have a consistent API experience, e.g. https://zalando.github.io/restful-api-guidelines/

Most importantly Swagger/OpenAPI gives us a "simple" (everything is relative!) language to define APIs and discuss/review them independent of languages as teams use different ones across Zalando Tech.