Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations (readOnlyHint=true, destructiveHint=false, idempotentHint=true) already establish safety. The description adds valuable behavioral detail: the timeline is reverse-chronological, newest first, capped at 50 events, and includes three most recent notes. No contradictions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.