Validates IBAN/ISBN/EAN/Luhn checksums and finds the one wrong digit
Install
Run one of the commands below, then add the client config underneath.
https://check-digit.gumballtools.com/api/mcpClient configuration
Paste into Claude Desktop, Cursor (mcp.json), VS Code or any MCP client, then restart the client.
{
"mcpServers": {
"check-digit": {
"url": "https://check-digit.gumballtools.com/api/mcp"
}
}
}About this server
Check Digit Validator is listed in the Other Tools category of the MCPNav directory. It is distributed as Streamable HTTP and can be loaded by any client that speaks the Model Context Protocol.
Typical uses include giving your assistant scoped access to the corresponding service so it can answer questions and take actions with real data instead of guessing. Always review what a server can access before you enable it — see our MCP security guide.
Frequently asked questions
What is the Check Digit Validator MCP server?＋
Check Digit Validator is an MCP server by gumballtools. Validates IBAN/ISBN/EAN/Luhn checksums and finds the one wrong digit
How do I install Check Digit Validator?＋
Install it with: https://check-digit.gumballtools.com/api/mcp. Then add the JSON config to your client's MCP settings and restart the client.
Is Check Digit Validator free to use?＋
The MCP server itself is free to install. The source is public on https://github.com/bwalvoord/gumball. Any third-party API it calls (such as a search or maps API) may require its own key and billing.
Which clients support Check Digit Validator?＋
Any MCP-compatible client can use it, including Claude Desktop, Cursor, VS Code, Windsurf and custom agents.