Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly=true, destructive=false and idempotent=true, so the safety profile is covered. The description nonetheless adds meaningful context beyond them: it clarifies no credits are spent and nothing is published, which is a valuable side-effect disclosure given the other automation tools in this family. It stops short of stating auth requirements or the media-link format.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.