Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful behavioral context by noting the 'newest first' ordering and instructing the agent to 'Follow any llmContext guidance included in results,' which is beyond what annotations or the schema express.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.