Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered and the bar is lower. The description adds the useful scoping detail that results come from the workspace directory, but says nothing about what is returned (names vs. paths) or whether results are recursive or filtered.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.