Setup with Claude Desktop

Configure jpx-server as an MCP server for Claude Desktop.

Prerequisites

1. Install jpx-server:

   cargo install jpx-server
   

   Or use Docker (no installation required).

2. Have Claude Desktop installed

Configuration

Docker (Recommended)

The simplest way to run jpx as an MCP server using the dedicated server image:

{
  "mcpServers": {
    "jpx": {
      "command": "docker",
      "args": ["run", "-i", "--rm", "ghcr.io/joshrotenberg/jpx-server"]
    }
  }
}

Available for linux/amd64 and linux/arm64.

macOS

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

{
  "mcpServers": {
    "jpx": {
      "command": "jpx-server"
    }
  }
}

If jpx-server is not in your PATH, use the full path:

{
  "mcpServers": {
    "jpx": {
      "command": "/Users/yourname/.cargo/bin/jpx-server"
    }
  }
}

Windows

Edit %APPDATA%\Claude\claude_desktop_config.json:

{
  "mcpServers": {
    "jpx": {
      "command": "C:\\path\\to\\jpx-server.exe"
    }
  }
}

Verify Setup

1. Restart Claude Desktop
2. Look for the jpx tools in Claude’s tool list
3. Try a simple query:

User: I have this JSON: {"users": [{"name": "alice"}, {"name": "bob"}]}
      Get all the names.

Claude: [Uses jpx.evaluate]
        Result: ["alice", "bob"]

Strict Mode

To use only standard JMESPath functions (no extensions):

{
  "mcpServers": {
    "jpx": {
      "command": "jpx-server",
      "args": ["--strict"]
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "jpx": {
      "command": "docker",
      "args": ["run", "-i", "--rm", "ghcr.io/joshrotenberg/jpx-server", "--strict"]
    }
  }
}

Troubleshooting

jpx-server not found

Make sure jpx-server is in your PATH, or use the full path in the config.

Tools not appearing

1. Check the config file syntax (must be valid JSON)
2. Restart Claude Desktop completely
3. Check Claude Desktop logs for errors

Permission errors on file access

The evaluate_file tool has security restrictions. It only allows access to files in safe directories (not system paths).