Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With one parameter at 100% schema description coverage ('Algorithm identifier: gcd, is_prime, or factorial'), the schema already fully documents the input. The description only restates the bounded set ('supported mathematical algorithm') without adding format or fallback semantics, so the baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.