Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the safe read-only, idempotent, non-destructive, closed-world profile, so the bar is lower. The description still adds useful traits: results are ordered newest first, entries are anonymised, and each carries a one-line summary and URL. It does not state any count cap or truncation behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.