JSON is trash, very unfriendly for human editing

the more complex you make the structure the less likely that it will be adequately handled by the majority of clients

you have to be able to form the data into the format that the hash that the signature is on, no matter how rearranged the fields are in the object, adding more fields leads to more chances of code failing to put it in the right order and not getting the matching hash

also did i mention that JSON sucks?

YAML would have been better