Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: results are pointers (document IDs plus source URLs) rather than full documents, which tells the agent to expect to chain into fetch. It doesn't disclose ranking, result limits, or query matching behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.