Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, non-destructive behavior, and the description adds a concrete behavioral trait beyond them: unknown or non-public UUIDs return not_found. It also clarifies the scope to public details of German flea markets, which is useful context for an agent selecting the tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.