Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only express readOnly/openWorld/destructive hints as false. The description adds meaningful behavior beyond that: it changes draft status to pending review, may set a scheduled publish time, and does not publish externally. This is valuable context not available in the schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.