Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only, idempotent and non-destructive behavior, so the bar is lower; the description goes beyond them by disclosing the privacy-minimal payload, that a PR Explanation result is durable and only available "once stored", and that Code Review returns status only. It does not state whether status partially completes, but the added behavioral context is real and non-obvious.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.