Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds the non-obvious behavioral detail that hidden files such as .env are omitted, which matters for discovery. No rate limits or pagination context, but those are minor for a tree listing.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.