Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description contributes the shape of the payload (family, default vs premium classification, per-size cost), which is useful context, but adds nothing on auth, market scope, or rate behavior. Adequate against the lower bar set by annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.