Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and closed-world. The description adds a trait annotations cannot express: no funds are spent, which is the crucial differentiator from the paid execution siblings. It also discloses the full return payload, which matters because there is no output schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.