Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and open-world, so safety is covered; the description adds the substantive behavior that the tool performs network resolution against UNPKG and that framework-managed packages are treated as errors when a framework is supplied or detected. This is real behavioral context beyond the structured fields.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.