Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond annotations (readOnlyHint=false, destructiveHint=false, idempotentHint=true), the description adds critical behavior: ownership enforcement ('you can only cancel your own subscriptions'), the deactivation mechanism ('the row is deactivated (not deleted)'), and the impact on historical events ('stay available via recent_alerts'). This fully explains the non-destructive, idempotent nature without contradicting annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.