Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the baseline is 3, but the description adds genuine meaning the schema does not: the $ref syntax '$ref:<operation-id>:<field>' is spelled out along with its semantics ('take a value from an earlier operation's first result'), whereas the schema only says a $ref string is allowed. It also summarizes the shaping options (select, filter, sort, limit, count_only) and the allowlisted GET path constraint, though it does not elaborate on filter operator behavior.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.