Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false. The description adds useful behavior beyond these: the operation is performed 'as the agent,' only allowed on activated threads, and belongs to a reply-first workflow. This is meaningful context without contradicting the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.