Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It correctly states that the tool returns a regex pattern, which implies a string output. However, it does not explain the behavior when card_type is omitted (default 'any'). The straightforward nature makes this acceptable.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.