Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false), the description adds key behavioral details: the action is not synchronous ('returns immediately'), cleanup is best-effort, and the sweeper will retry on failure. This provides useful transparency.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.