I think it's a good start but the draft could need some more work w.r.t to clarity:
- is it allowed to define other fields ad-hoc?
- If yes, where to register these fields?
- rationale: why are we doing this? Give two, three use-cases (just makes it clearer for the user what cool things he/she could do with that format)
- what fields are a MUST?
I think it's a good start but the draft could need some more work w.r.t to clarity: