Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the transparency burden. It discloses cursor-based polling, which is useful, but does not state whether reading mutates state (e.g., marks messages as read), whether messages persist after being read, or any auth/rate-limit behavior. This is adequate but not fully transparent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.