The JSON schema ecosystem is a mess. json-schema.org is one thing, openapi is another (it uses an 'extended subset' of json-schema.org, which is another way of

The JSON schema ecosystem is a mess. json-schema.org is one thing, openapi is another (it uses an 'extended subset' of json-schema.org, which is another way of saying 'incompatible'), there’s also typeschema, and a bunch of other pet projects. There is no official JSON schema RFC, there is no official linking between json-schema.org and the JSON RFC. There is no push to make every language that supports JSON to also support a JSON schema system. Finally, there isn't even a guarantee that all human-readable JSON document specifications can be expressed within a JSON schema in any sensible way.