Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare non-read-only, non-destructive, closed-world behavior, and the description adds genuinely new context: the stop is graceful and results remain readable for 5 minutes until automatic cleanup. That lifecycle detail is not derivable from the annotations and materially affects follow-up behavior. It doesn't state what happens if the sessionId is invalid or already stopped.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.