Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish read-only, non-destructive, closed-world behavior, so the bar is lower. The description still adds real value beyond them: it discloses that the tool returns a ranked recommendation and loop decision, that it is free, and that it performs no execution — an agent knows it is safe to call and produces advice, not side effects.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.