Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and destructiveHint false, so the safety profile is known. The description adds valuable behavioral details: case-insensitive partial matching, root default, and returned fields (path, type, size), which go beyond the structured annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.