Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema descriptions cover all parameters (100%), so the baseline is 3. The description adds value by specifying the content field as the payload location, emphasizing 'no file', and introducing the 300,000-character limit, which is not present in the schema. This supplements the parameter meaning beyond the schema alone.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.