> The practical alternative is to use JSON everywhere, possibly with some additional tooling to generate code from a JSON schema.

Protobuf has a bidirectional JSON mapping that works reasonably well for a lot of use cases.

I have used it to skip the protobuf wire format all together and just use protobuf for the IDL and multi-language binding, both of which IMO are far better than JSON-Schema.

JSON-Schema is definitely more powerful though, letting you do things like field level constraints. I'd love to see you tomorrow that paired the best of both.