Nip Checker

A Model Context Protocol (MCP) server for checking Polish NIP (Tax Identification Numbers) using the official Ministry of Finance VAT taxpayer database.

Features

• ✅ Real-time NIP verification using official Polish Ministry of Finance API
• ✅ Bank account verification - check if bank account belongs to specific NIP
• ✅ Automatic date handling - defaults to current date
• ✅ Input normalization - handles NIP formats with or without hyphens
• ✅ Comprehensive error handling and validation
• ✅ Ready for Claude Desktop - works seamlessly with AI assistants

Quick Start with npx (Recommended)

Add this to your Claude Desktop configuration:

{
  "mcpServers": {
    "nip-checker": {
      "command": "npx",
      "args": ["-y", "@solverio-pl/nip-checker-mcp@latest"]
    }
  }
}

Installation Options

Option 1: Direct npx usage (No installation needed)

npx @solverio-pl/nip-checker-mcp@latest

Option 2: Global installation

npm install -g @solverio-pl/nip-checker-mcp
nip-checker-mcp

Option 3: Local development

git clone https://github.com/solverio-pl/nip-checker-mcp.git
cd nip-checker-mcp
npm install
npm run build
npm start

Available Tools

check_nip

Verify Polish NIP in the VAT taxpayer database.

Parameters:

• nip (required): Polish NIP number (10 digits, hyphens optional)
• date (optional): Date for verification (YYYY-MM-DD format, defaults to today)

Example:

Check NIP 9491626103

check_nip_bank_account

Verify if a bank account is assigned to a specific NIP.

Parameters:

• nip (required): Polish NIP number (10 digits)
• bankAccount (required): Bank account number (26 digits)
• date (optional): Date for verification (YYYY-MM-DD format)

Example:

Verify if account 38109017950000000151316514 belongs to NIP 9491626103

Sample Output

✅ NIP Verification Results

**NIP**: 9491626103
**Company**: JANUSZ CHALIMONIUK
**VAT Status**: Czynny (Active)
**Address**: BURSZTYNOWA 73D, 42-202 CZĘSTOCHOWA
**Registration Date**: 2022-09-01
**Bank Accounts**: 38109017950000000151316514
**REGON**: 240070517
**Virtual Accounts**: No

**Request Details**:
- Request ID: rLtV8-9471ak2
- Query Date: 02-08-2025 09:29:38

Claude Desktop Configuration

Windows

Edit: %APPDATA%\Claude\claude_desktop_config.json

macOS

Edit: ~/Library/Application Support/Claude/claude_desktop_config.json

Full configuration example:

{
  "mcpServers": {
    "nip-checker": {
      "command": "npx",
      "args": ["-y", "@solverio-pl/nip-checker-mcp@latest"]
    }
  }
}

Personal Settings Addition

Add this simple line to your Claude personal settings for automatic usage:

NIP Checker: When user asks to check/verify/lookup a Polish NIP number, use the check_nip MCP tool automatically.

Usage Examples

Once configured, you can simply ask:

• "check nip 9491626103"
• "verify nip 123-456-78-90"
• "lookup nip 9491626103 for yesterday"
• "is account 38109017950000000151316514 assigned to nip 9491626103?"

API Source

This tool uses the official Polish Ministry of Finance API:

• Base URL: https://wl-api.mf.gov.pl/
• Documentation: Available at the API endpoint
• Data Source: Official VAT taxpayer registry ("Biała Lista Podatników")

Requirements

• Node.js 18.0.0 or higher
• Internet connection for API access

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

For issues and feature requests, please use the GitHub Issues page.

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Made with ❤️ by Solverio for the Polish business community.