Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare read-only, idempotent, non-destructive behavior, so the description's main value is adding sort order ('newest activity first'), return contents ('who it is and the last message'), and cost ('Free'). It does not explain pagination behavior, how limit/before interact, or whether status filtering changes the default result set.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.