Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds meaningful context beyond that: the output is explanatory reference content rather than a binding determination, and the input must be an ISO alpha-2 code. No permission, rate-limit, or failure-mode detail is given, but none is expected for a static lookup.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.