Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: the stored blob is encrypted and decryption must happen client-side, which tells the agent not to expect plaintext back. It does not mention auth (though the schema covers api_key).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.