Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
readOnlyHint=true is consistent with a dry-run/inspection operation. Beyond the annotation, the description usefully discloses what the tool reports back (shipped files, junk and secret warnings, registry check), which is meaningful because there is no output schema. It does not say whether warnings block anything or how failures surface.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.