XML does not have support for schemas either. XML Schemas is a separate spec (and actually not the only one, there were few competing ones). I'd use JSON schem

XML does not have support for schemas either. XML Schemas is a separate spec (and actually not the only one, there were few competing ones). I'd use JSON schema over XML schema any day. And I read and wrote many XML schemas and still do sometimes. JSON schema actually built by sane people. If that required a decade, so be it.