Rejestr.io MCP Server

A Model Context Protocol (MCP) server providing access to Poland's largest business registry database - rejestr.io.

📋 What is this?

This MCP server enables AI assistants and applications to:

• 🔍 Search companies by name, NIP (Tax ID), or KRS (Court Register)
• 🏢 Retrieve detailed company information
• 👥 Check real beneficiaries from CRBR (Central Register of Real Beneficiaries)
• 🔗 Analyze connections between companies and individuals
• 📊 Access financial documents and statements
• 📄 Browse KRS (National Court Register) records

🎯 Choose Your Setup

👤 Are you a Claude Desktop user? → Jump to Claude Desktop Setup

👨‍💻 Are you a developer/want local control? → Jump to Developer Setup

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👤 For Claude Desktop Users

This section is for non-technical users who want to use this MCP server with Claude Desktop app.

Step 1: Get rejestr.io API Key

1. Register at rejestr.io
2. Purchase an API plan (various options available)
3. Copy your API key from the user panel

Step 2: Install Python

1. Download Python 3.13 or newer from python.org
2. During installation, check "Add Python to PATH"
3. Verify installation by opening terminal and typing:

   python --version
   

Step 3: Download and Configure Server

1. Download this repository (green "Code" button → "Download ZIP") and extract it
2. Create a .env file in the main project folder with your API key:

   REJESTR_IO_API_KEY=your_api_key_here
   

Step 4: Configure Claude Desktop

1. Open Claude Desktop config file:

   • Windows: %APPDATA%\Claude\claude_desktop_config.json
   • macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
   • Linux: ~/.config/Claude/claude_desktop_config.json

2. Add this configuration (replace PATH_TO_PROJECT with full path to project folder):

   Windows:

   {
     "mcpServers": {
       "rejestr-io": {
         "command": "python",
         "args": ["-m", "rejestr_io_mcp"],
         "cwd": "C:\\Users\\YourName\\rejestr-io-mcp",
         "env": {
           "PYTHONPATH": "C:\\Users\\YourName\\rejestr-io-mcp"
         }
       }
     }
   }
   

   macOS/Linux:

   {
     "mcpServers": {
       "rejestr-io": {
         "command": "python3",
         "args": ["-m", "rejestr_io_mcp"],
         "cwd": "/home/your_name/rejestr-io-mcp",
         "env": {
           "PYTHONPATH": "/home/your_name/rejestr-io-mcp"
         }
       }
     }
   }
   

3. Save the file and restart Claude Desktop

Step 5: Test It

Open Claude Desktop and ask:

Check my rejestr.io account balance

If everything works correctly, Claude should return your account balance information.

🐛 Troubleshooting (Claude Desktop)

Claude doesn't see the tools:

1. Verify paths in claude_desktop_config.json are correct
2. Make sure .env file contains valid API key
3. Restart Claude Desktop completely

Authorization error:

1. Check if API key in .env is correct
2. Verify your API plan is active at rejestr.io
3. Check account balance

Import errors:

1. Ensure Python is installed correctly
2. Check Python version: python --version (requires 3.13+)
3. Try reinstalling: pip install httpx python-dotenv mcp

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👨‍💻 For Developers / Local Usage

This section is for developers who want to integrate this MCP server with custom agents, applications, or use it locally.

Quick Start

# Clone the repository
git clone https://github.com/your-user/rejestr-io-mcp.git
cd rejestr-io-mcp

# Create virtual environment (recommended)
python -m venv .venv
source .venv/bin/activate  # Linux/macOS
# or
.venv\Scripts\Activate.ps1  # Windows PowerShell

# Install dependencies
pip install -e .

# Create .env file with your API key
echo "REJESTR_IO_API_KEY=your_api_key_here" > .env

Local Testing

# Run server in stdio mode
python -m rejestr_io_mcp

# Use MCP Inspector for interactive testing
npx @modelcontextprotocol/inspector python -m rejestr_io_mcp

Integration with Custom Agents

The server communicates via stdio using the Model Context Protocol. Example integration:

import asyncio
from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client

async def run_agent():
    server_params = StdioServerParameters(
        command="python",
        args=["-m", "rejestr_io_mcp"],
        env={"REJESTR_IO_API_KEY": "your_key_here"}
    )
    
    async with stdio_client(server_params) as (read, write):
        async with ClientSession(read, write) as session:
            await session.initialize()
            
            # List available tools
            tools = await session.list_tools()
            print(f"Available tools: {[tool.name for tool in tools.tools]}")
            
            # Call a tool
            result = await session.call_tool(
                "get_company_info_using_nip",
                arguments={"nip": "5252408074"}
            )
            print(result)

asyncio.run(run_agent())

Project Structure

rejestr-io-mcp/
├── rejestr_io_mcp.py      # Main MCP server implementation
├── pyproject.toml          # Project configuration & dependencies
├── .gitignore             # Git ignore file
└── README.md              # This documentation

Environment Variables

• REJESTR_IO_API_KEY (required) - Your rejestr.io API key

Dependencies

• Python 3.13+
• httpx >= 0.28.1 - Async HTTP client
• mcp >= 1.25.0 - Model Context Protocol SDK
• python-dotenv - Environment variable management

API Endpoints Used

All endpoints use https://rejestr.io/api/v2 base URL:

• GET /org?nazwa={name} - Search companies
• GET /org/{krs} - Get company by KRS
• GET /org/nip/{nip} - Get company by NIP
• GET /org/{krs}/crbr - Get beneficiaries
• GET /org/{krs}/krs-powiazania - Get company connections
• GET /osoby/{id} - Get person data
• GET /osoby/{id}/krs-powiazania - Get person connections
• GET /org/{krs}/krs-rozdzialy/{chapter} - Get KRS chapter
• GET /org/{krs}/krs-dokumenty - List financial documents
• GET /org/{krs}/krs-dokumenty/{doc_id}?format=json - Get financial statement (costs 0.50 PLN)
• GET /konto/stan - Check account balance

Adding to Other MCP Clients

For Cline (VSCode extension): Add to your VSCode settings:

{
  "mcp.servers": {
    "rejestr-io": {
      "command": "python",
      "args": ["-m", "rejestr_io_mcp"],
      "cwd": "/path/to/rejestr-io-mcp"
    }
  }
}

For custom applications: Use the MCP SDK to connect to the server via stdio transport.

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🛠️ Available Tools

Company Search

• get_company_info_using_name - Search company by name

  Find information about "CD Projekt" company
  

• get_company_info_using_nip - Get company data by NIP (Tax ID)

  Show company with NIP 5252408074
  

• get_company_info_using_krs - Get company data by KRS number

  What are the details of company KRS 0000012345?
  

Detailed Information

• get_company_krs_documentation - Get specific KRS chapter

  • Available chapters: ogolny, oddzialy, akcje, wzmianki, zobowiazania, przeksztalcenia

  Show general chapter from KRS for company 0000012345
  

• get_person_data - Get person information

  Show data for person ID 123456
  

Beneficiaries and Connections

• get_beneficiary - List of real beneficiaries from CRBR

  Who is the beneficiary of company KRS 0000012345?
  

• get_connections_by_krs - Company connections

  Show all connections for company KRS 0000012345
  

• get_connections_by_person - Person connections

  In which companies does person ID 123456 operate?
  

Financial Documents

• get_financial_documents - List of financial documents

  Show available financial statements for KRS 0000012345
  

• get_financial_statement_in_json - Download statement (costs 0.50 PLN)

  Download financial statement document ID 789 for KRS 0000012345
  

Account Management

• get_token_amount - Check account balance

  How much credit do I have on my rejestr.io account?
  

💡 Usage Examples

Company Analysis

Find "Allegro" company and show:
1. Basic information
2. Real beneficiaries
3. All connections with other companies

Due Diligence

For company KRS 0000012345 check:
- Is it in liquidation or bankruptcy
- Who is the real beneficiary
- What connections it has with other entities
- Latest financial statements

Person Analysis

Find Jan Kowalski in company X, then show all companies 
where this person holds any position

📝 Important Notes

• ⚠️ Costs: Downloading financial statements in JSON costs 0.50 PLN per document, rest operations are cost per usage.
• 🔐 Security: Never share your API key. The .env file should be in .gitignore
• 📊 Limits: Check your API plan limits at rejestr.io
• 🔄 Updates: Data in rejestr.io is regularly updated from official registries

📚 Additional Resources

• rejestr.io API Documentation
• Model Context Protocol Specification
• Claude Desktop Documentation

📄 License

MIT License - feel free to use, modify, and distribute this code.

🤝 Contributing

Bug reports and pull requests are welcome!

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Made with ❤️ for the Polish business data community