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90
MCP live MCP 2026-07-28 streamable-http

Check Digit Validator

com.gumballtools/check-digit

Validates IBAN/ISBN/EAN/Luhn checksums and finds the one wrong digit

Watch this dependency Share evidence report
Uptime
100.0%
5 direct probes · 30d
Response
1375ms
last probe
Tools
1
callable
Resources
0
readable
Prompts
0
available
Primary URL
https://check-digit.gumballtools.com/api/mcp
Score: 90/100
Handshake verified by our own probe.
pass Answers the MCP handshake 50/50
The handshake and the list calls succeeded on the primary URL.
pass Lists tools, resources or prompts 30/30
1 tools, 0 resources, 0 prompts returned.
partial 3 or more catalogue items 0/10
1 item in total; 3 or more earns these points.
How to earn +10 points
Expose at least three tools, resources or prompts
Split a catch-all tool into focused ones, or publish your docs and templates as resources and prompts.
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pass Describes itself 10/10
68 characters; more than 30 earns these points.

Tools · 1

run

Validate the check digit(s) on an IBAN, ISBN-10, ISBN-13, EAN-13, UPC-A, or Luhn-checked card number, and when it fails, try to say which digit is wrong. Use this instead of computing the checksum yo…

How to use

Claude Desktop or claude.ai: add a custom connector (Customize → Connectors; on Team and Enterprise plans an owner adds it under Organization settings → Connectors) with this server URL: https://check-digit.gumballtools.com/api/mcp

Cursor or Cline: add to your MCP config:

{
  "mcpServers": {
    "check_digit_validator": {
      "url": "https://check-digit.gumballtools.com/api/mcp",
      "transport": "streamable-http"
    }
  }
}