Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already mark the tool as read-only and idempotent, so the description's job is lighter. It adds value by disclosing that the tool provides only a brief of evidence and threshold logic and that actual thresholds and assessments always come from Senlay Core, which manages expectations about the authority of the returned information.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.