Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds value by disclosing the returned fields, which matters because no output schema exists. It stops short of stating auth requirements or error behavior, but for a read-only self-lookup that is minor.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.