check-digit.gumballtools.com

Very long descriptions are sometimes used to bury instructions to the AI. Skim it before allowing.

This server isn't on gate's handpicked list. That's not necessarily bad, but there's no third-party signal about it — review its tools carefully.

The tool performs a well-scoped, deterministic checksum validation for a fixed set of numeric formats (IBAN, ISBN, EAN, UPC, Luhn). The description is verbose but stays on-topic, doesn't instruct the agent to hide actions, doesn't request secrets/credentials/files, and doesn't exfiltrate data externally. Input schema is appropriately constrained. No spoofing of another tool's identity. No action needed.