Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only declare destructiveHint=false, so the description carries most of the behavioral burden and does so well: it discloses login requirement, possible step completion, next-step scheduling, adding people, LLM consumption, notifications, and lack of a durable request dedup key. That is meaningful context beyond what the annotation provides.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.