Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the safety profile (not read-only, idempotent, non-destructive, open-world), so the bar is lower. The description adds meaningful context beyond them: the thread must already be resolved, and the caller acts 'as its owner', implying an ownership/authorization requirement that the annotations do not convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.