Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does add real value by disclosing that pending deliveries are also dropped — a non-obvious side effect. However, it never states that deletion is irreversible, what happens if the webhook_id does not exist, or whether any auth scope is required.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.