Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description must compensate. It explains that 'completed' is a list of unit IDs and 'subject' indicates the subject area, and it reveals the logic (prerequisites are met). This adds meaning beyond the bare schema, though it doesn't specify formats or how to identify the subject uniquely.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.