Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, and the description is consistent with that but adds nothing. It does not disclose whether marking read is reversible (via update_watching), whether the watchId must exist or be owned by the caller, or what the response contains. With annotations covering the safety profile, a terse restatement earns little.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.