I'm using https://cuelang.org for data / config schemas. Dhall is another good choice that is more mature
I wish https://sdlang.org/ had more widespread use. IMO it’s the perfect mix of native types, terse syntax, and no surprises like functions in config, or significant white space, etc.
Cue is nice because it unifies your files and tells you of they are valid, in the sense that they make sense and do not conflict. The ability to add constraints is huge