Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Adds real context beyond annotations: a per-request daily rate limit, a $0.02 per-call charge, and a no-charge-on-failure policy — the last is especially useful for a non-idempotent, externally-facing email action. It does not say what happens when nobody is left to sign or whether completed/cancelled requests error out.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.