Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Adds substantial behavior beyond the annotations, which only cover safety and idempotency: it discloses the cost model (1 check per keyword, '12 keywords = 12 checks'), the scope (Google top 100, tracker's location and language), and the expected latency ('20 minutes or more'). This is exactly the operational context an agent needs before firing a slow, non-idempotent job.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.