Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The schema already covers plan_id thoroughly with a regex pattern, length, and source description, so the baseline is high. The description adds value with 'DO NOT guess or enumerate plan IDs', an explicit example call, and a clear statement that only user-supplied or tool-supplied IDs are valid, which strengthens anti-hallucination behavior.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.