Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate read-only, idempotent, open-world behavior. The description adds value by specifying the timeline granularity (per-frame, per-minute) and event types, which are behavioral details not captured by annotations. No contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.