Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered without the description. The description does add one piece of behavioral context, 'principal-scoped,' implying access is limited to the calling principal, which is useful beyond the annotations, but it stops there.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.