Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only declare the safety profile (destructiveHint false, idempotentHint false); the description adds behavior they cannot express: the saved algorithm is preserved, the action is reversible, and deactivation does not flatten broker exposure. That last point is a high-value operational caveat.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.