Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the full safety profile (not read-only, non-destructive, idempotent, closed-world), so the description only needs to add effect-level context. It does say the messages leave the inbox and land in the archive, but is silent on reversibility (restore_emails exists), permission requirements, and partial-failure behavior when some IDs are invalid.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.