Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, covering safety. The description adds useful behavior beyond annotations: it returns only paths, not contents, and names typical Astro directories. It does not discuss pagination or ordering, but the output schema and read-only nature reduce the need for that detail.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.