I spent the last year and half working on a project where we planned to use OpenApi/AsyncApi to generate typed api clients and validate api requests between all our services and applications (written in typescript & C#).

Going into it, I thought we'd be on a well traveled path, but that was far from the case...

Typescript has some decent code generation packages (although fragmented) and request validation can be hacked via AJV... But tooling around C# was halfbaked at best.

In the end, I didn't really feel like OpenApi provided the API "contract" I had originally hoped for.

If I could start over, I would probably use something like gRPC for internal service communication (would maybe still use OpenAPI for any public API)