Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), and the description adds real value on top: sort order (by path), returned fields (submission timestamps, warning/error counts, submitted URL count by content type), and the notable quirk that indexed is null because Google deprecated it. That deprecation note prevents an agent from misinterpreting a null field. It stops short of anything about permissions or call cost, hence a 4.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.