Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With annotations already declaring readOnly, idempotent, and non-destructive behavior, the description adds valuable context: the archive is first-hand only, carries publish date/topic/source URL/summary, is Chinese-language, and is not the account's full history. The clarification of 'A-grade' and the coverage window give an agent accurate expectations not inferable from annotations alone.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.