Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does well: it discloses rate limiting (5 checks per caller per day), that no API key or auth is needed, the 5000-char input ceiling, and the shape of the response (0-100 score with located tells and fix hints). It stops short of stating failure modes or what happens when the quota is exhausted.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.