Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-open-world), and the description adds genuine edge-case behavior: duplicate IDs are deduplicated and unknown UUIDs are silently skipped. This tells the agent to expect partial results rather than an error, which is valuable context beyond the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.