Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly/idempotent/openWorld/non-destructive, and the description adds real value beyond them: metered usage tied to the connected account, one bounded request with no polling or retry, affiliate 27 exclusion, and the warning not to infer coverage from an empty result.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.