Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description goes beyond annotations: it explains the toggle behavior (adding and removing), the deterministic anonymous ID mechanism, and that no API key is needed. These are behavioral details not captured in the annotations, which only mark destructiveHint. The description also clarifies identity consistency, which is valuable for the agent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.