Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations mark this as a non-read-only, non-idempotent write, and the description adds genuinely new behavior: the message is delivered to a human team, it requires explicit user consent, and it does not consume the daily quota. The rate-limit and consent semantics go well beyond what the structured fields convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.