Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds useful behavioral context beyond that: the response is a signed, read-only URL and the package's contents (facts, calculated facts, offer/decline with files), which is genuinely informative about the artifact.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.