Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description earns credit for adding behavior beyond them: it returns a download resource link on completion and deliberately withholds the internal job identifier. This gives the agent real expectations about the response's shape and security posture.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.