IMHO, it would be helpful if the specification included a section where all reserved words were listed, with short explanations and references.

An example:

• data -- mandatory attribute for the list of primary data; reserved key for the top-level request and response objects (details)
• id -- mandatory attribute for every resource object; pair (id,type) forms unique (per-response) composite key of a resource; reserved key for resource objects (details)
• ...