Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true, idempotentHint=false and readOnlyHint=false, so 'permanently' largely restates structured data. The description adds nothing about cascade effects (e.g. what happens to documents in the deleted library), permission requirements, or confirmation behavior that the annotations do not already convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.