Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly, idempotent, non-destructive and closed-world, so safety is settled. The description adds genuinely new context: it is a 'static reference; no project data,' telling the agent the result is independent of project state and safe to call speculatively — a meaningful behavioral disclosure.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.