Japanese Postal Code Lookup MCP server

The Zipcode Search MCP Server provides Japanese postal code to address lookup functionality through the Model Context Protocol (MCP). This server enables AI assistants and other MCP clients to search for Japanese addresses using 7-digit postal codes by leveraging the Zipcloud API.

Installation

Prerequisites

• Python 3.10 or higher
• uv (recommended) or pip

Setup Instructions

1. Clone the repository:

   git clone https://github.com/rooking-oss/zipcode-search-mcp.git
   cd zipcode-search-mcp
   

2. Install dependencies using uv:

   uv sync
   

   Or with pip:

   pip install -e .
   

3. Run the MCP server:

   uv run python main.py
   

Client Configuration

Claude Desktop

Add the following configuration to your claude_desktop_config.json:

{
  "mcpServers": {
    "zipcode-search": {
      "command": "uv",
      "args": ["run", "python", "/path/to/zipcode-search-mcp/main.py"]
    }
  }
}

Other MCP Clients

For other MCP clients, use the following connection details:

• Server Name: zipcode-search
• Command: uv run python main.py
• Working Directory: Project root directory

Using the Tool

Search Zipcode Tool

The server provides a single tool through the MCP protocol:

• Tool name: search_zipcode
• Description: Searches for a Japanese address using a postal code
• Parameters:
  • zipcode (string): 7-digit postal code (e.g., "1000001")
• Returns:
  • address (string): The found address, or "Address not found" if no match

Example Usage

In your MCP client (like Claude), you can use natural language:

What's the address for postal code 1000001?

Or directly invoke the tool:

Use the search_zipcode tool to find the address for postal code 1600020

Troubleshooting

Server Won't Start

1. Verify Python version is 3.10+:

   python --version
   

2. Ensure dependencies are installed:

   uv sync
   

3. Check if the server starts manually:

   uv run python main.py
   

Postal Code Not Found

• Ensure the postal code is exactly 7 digits (no hyphens)
• Verify the Zipcloud API is accessible
• Check your internet connection

MCP Client Connection Issues

• Verify the path in your MCP client configuration is correct
• Ensure the server is executable from the specified directory
• Check MCP client logs for detailed error messages

How to install this MCP server

For Claude Code

To add this MCP server to Claude Code, run this command in your terminal:

claude mcp add-json "zipcode-search" '{"command":"uv","args":["run","python","main.py"]}'

See the official Claude Code MCP documentation for more details.

For Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > Tools & Integrations and click "New MCP Server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "zipcode-search": {
            "command": "uv",
            "args": [
                "run",
                "python",
                "main.py"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explicitly ask the agent to use the tool by mentioning the tool name and describing what the function does.

For Claude Desktop

To add this MCP server to Claude Desktop:

1. Find your configuration file:

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

2. Add this to your configuration file:

{
    "mcpServers": {
        "zipcode-search": {
            "command": "uv",
            "args": [
                "run",
                "python",
                "main.py"
            ]
        }
    }
}

3. Restart Claude Desktop for the changes to take effect