I like GraphQL schema, but it would have to have a standardized serialization aspect. Moreover, it really is designed for querying and has a bunch of stuff totally irrelevant to data.

But I agree ... I almost wish they'd finish it off and go for full on serialization.

That said, it may not be that-that hard, a serialization spec can be pretty short if need be. Certainly one could 'roll one's own' for a mid-sized project if need be.