Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and destructiveHint, so the description adds value by specifying the exact return scope: loop info and chapter node titles, with explicit exclusion of chapter content. It also adds the access rule that any active loop is navigable by anyone.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.