Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond the annotations, which only declare the write/destructive/open-world/idempotent profile. The description discloses the unconfirmed-send failure mode, warns against creating a replacement to retry, explains the expectedUpdatedAt concurrency guard, and gives an app-only recovery path (Activity > check status > confirm no post) — exactly the behavioral context annotations cannot carry.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.