MCP Server

Check Digit Validator MCP Server

com.gumballtools/check-digit

What is the Check Digit Validator MCP server?

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

Copy-paste configuration for popular MCP clients.

transport: http

Config generated by PluginBench — verify against the source before use.

~/.cursor/mcp.json

{
  "mcpServers": {
    "check-digit": {
      "url": "https://check-digit.gumballtools.com/api/mcp"
    }
  }
}

Convert colours between hex, RGB, HSL, OKLCH and CMYK, and compute harmonies.

Estimate a due date from LMP, conception, or ultrasound, with ACOG redating rules.

Step-by-step solver for linear/quadratic equations in one variable, signs and ± always right.

ISO 8601 week numbers: date to week, week to date, weeks-per-year.

Convert JSON samples into TypeScript interfaces and Zod schemas, with inference caveats.

Validate JSON, YAML, XML and CSV with exact line/column errors and silent-corruption warnings.