Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes beyond the destructiveHint annotation by disclosing that the action is irreversible ('cannot be undone'), that it commits both sides by creating a Handshake, and that user confirmation is required before execution. That is exactly the behavioral context a mutation tool needs.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.