any json data validation library recommendation?

[Maciej Dziardziel]

Hi

I'm writing json data validation tool in a language other than python,
but knowing that there is plenty of good tools for it,
I am looking for inspiration here.

I am aware of json schema standard, but on its own its
rather verbose and I'd rather have models defined in code
(directly or via some DSL).
Can anyone recommend library that provides
good API for declaring data schemas, so I could see how it could be done?

(Doing it is not a problem. Doing it in a way that's convenient for users,
readable and generates good error messages is something I care about).

Thanks
-- 
Maciej Dziardziel
fiedzia at gmail.com