Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full responsibility for disclosing behavior. It only states the action ('Deletes') without mentioning irreversibility, permissions, error handling, or side effects. The agent is not informed that deletion is permanent or what happens if the message does not exist.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.