"Optional" fields not noted in documentation.

[nicholasknight]

objects.md fails to note that the following fields may be absent from responses:

User:

• description
• app_data

Post:

• annotations
• reply_to

(Or feel free/encouraged to re-characterize this as "API omits fields contrary to documentation" -- personally, I don't much care for omitted fields in APIs and object specs, rather than simply empty or null fields.)