Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is fully covered without the description. The description adds the cross-tool context that slugs feed other tools' filters, which is useful, but says nothing about result size, ordering, or auth needs.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.