Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile needs no restating. The description adds one genuinely non-obvious behavioral note — that observed state transitions do not imply immediate agent change — which manages expectations in a way annotations cannot. It stops short of saying whether state is polled, final, or how stale it may be.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.