I don't think it is doing the validations on the client side for requests or responses, though it certainly could. I would tend to agree that this would be really useful, but would probably be a good thing to have configurable (so you could run it in dev/test/staging but maybe not prod).
Looks like that is exactly logic that is needed to make these validations. But it is in committee gem, which is a set of rack middlewares, and because of it, depending on it here and using its inner classes would be strange to me.
Do you think it is a valid point to extract this logic somewhere else and re-use it here and in committee ? Something along the lines of json-schema-support or json-schema-validators gem.
I don't see a huge perf benefit of blocking requests before they reach the server if they don't meet the json schema requirement. Maybe some sort of a debug or lint mode would be interesting. This issue has been open for 5 years with no movement, let's close it. If there's a very compelling future reason then we can open a new issue or re-open this one.