I wish the Cue docs were better. I arrived here https://cuelang.org/docs/usecases/configuration/ https://cuelang.org/docs/usecases/configuration/ but it doesn’t

I wish the Cue docs were better. I arrived here https://cuelang.org/docs/usecases/configuration/ https://cuelang.org/docs/usecases/configuration/ but it doesn’t answer basic questions like “can I define my own validation functions (the > < != operators used in the example)?”.