Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish this as a read-only, idempotent, non-destructive, closed-world read, so the bar is lower. The description still adds real behavioral context by enumerating the possible timing semantics (always, state_gated, never) and explaining that defaults are surfaced when the business has not configured anything, which prevents misreading an empty result.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.