Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and idempotentHint=true, so the bar is lower, yet the description still adds real value: passes dropped are permanently lost ("never made up later") and partial failures surface per-item in "failed". "Safe to retry" corroborates the idempotency hint. It does not, however, say what permissions are required.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.