caniuse is an extremely popular website among people that had to touch web technologies, so much that almost anyone searching for issues on web apis seriously will have hard time not stumble upon it very quickly.
Hence, it's a totally valid assomption that the HN crowd might be aware of it. I'm sorry you were not, but you really are an outlier on this, which is really not a bad thing, btw.
Thanks for the reply, but I've read HN almost daily for years and have been a professional developer for way longer than that. I also just finished an API-definition project that involved a ton of research on API design and code-generation tooling (with OpenAPI in particular).
I have never heard of "caniuse." Swagger? Postman? Mocking tools and services? Lots of their ilk? Sure. In fact just recently I saw this API article posted here: https://news.ycombinator.com/item?id=40161794
Hence, it's a totally valid assomption that the HN crowd might be aware of it. I'm sorry you were not, but you really are an outlier on this, which is really not a bad thing, btw.