Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the schema already documents session_id, timeout, not_etag, and modified_since. The description adds only a little: it reinforces that session_id drives repeated polling, but does not explain how not_etag or modified_since interact with repeat polls beyond what the schema states, so the baseline of 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.