Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnly, openWorld, idempotent, non-destructive, so the safety bar is low. The description still adds real behavioral context: results are 'read live' (not cached/stale), there is no auth or cost barrier ('Free, no sign-in'), and the response includes concrete remediation lines—details an agent could not infer from the annotations alone.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.