Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and readOnlyHint=false, so the description doesn't need to restate basic safety. It adds context that deletion is intended for stale or sensitive data, which helps the agent reason about consequences. No contradiction with annotations, but it could explicitly state permanence or error behavior for non-existent keys.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.