freecad-robust-mcp-fc111/docs/getting-started/configuration.md

Configuration

Configure the FreeCAD Robust MCP Server using environment variables and MCP client settings.

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Environment Variables

Variable	Description	Default
FREECAD_MODE	Connection mode: xmlrpc, socket, or embedded	xmlrpc
FREECAD_PATH	Path to FreeCAD's lib directory (embedded mode only)	Auto-detect
FREECAD_SOCKET_HOST	Socket/XML-RPC server hostname	localhost
FREECAD_SOCKET_PORT	JSON-RPC socket server port	9876
FREECAD_XMLRPC_PORT	XML-RPC server port	9875
FREECAD_TIMEOUT_MS	Execution timeout in ms	30000

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Connection Modes

The Robust MCP Server supports three connection modes:

Mode	Description	Platform Support
xmlrpc	Connects to FreeCAD via XML-RPC (port 9875)	All platforms (recommended)
socket	Connects via JSON-RPC socket (port 9876)	All platforms
embedded	Imports FreeCAD directly into process	Linux only (crashes on macOS/Windows)

XML-RPC Mode (Recommended)

The default and recommended mode. Works on all platforms.

export FREECAD_MODE=xmlrpc
freecad-mcp

Socket Mode

Alternative to XML-RPC using JSON-RPC over TCP sockets.

export FREECAD_MODE=socket
freecad-mcp

Embedded Mode (Linux Only)

!!! warning "Linux Only" Embedded mode only works on Linux. On macOS and Windows, it will crash because FreeCAD's FreeCAD.so library links to its bundled Python, which conflicts with external Python interpreters.

Embedded mode imports FreeCAD directly into the Robust MCP Server process for fastest execution.

export FREECAD_MODE=embedded
export FREECAD_PATH=/usr/lib/freecad/lib
freecad-mcp

Note: Embedded mode testing is minimal. For production use, prefer xmlrpc or socket modes.

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MCP Client Configuration

Claude Code / Claude Desktop

Add to ~/.claude/claude_desktop_config.json or a project .mcp.json file:

{
  "mcpServers": {
    "freecad": {
      "command": "freecad-mcp",
      "env": {
        "FREECAD_MODE": "xmlrpc"
      }
    }
  }
}

If installed from source with mise/uv:

{
  "mcpServers": {
    "freecad": {
      "command": "/path/to/mise/shims/uv",
      "args": ["run", "--project", "/path/to/freecad-robust-mcp-and-more", "freecad-mcp"],
      "env": {
        "FREECAD_MODE": "xmlrpc"
      }
    }
  }
}

Docker Configuration

{
  "mcpServers": {
    "freecad": {
      "command": "docker",
      "args": [
        "run", "--rm", "-i",
        "-e", "FREECAD_MODE=xmlrpc",
        "-e", "FREECAD_SOCKET_HOST=host.docker.internal",
        "spkane/freecad-robust-mcp"
      ]
    }
  }
}

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GUI vs Headless Mode

FreeCAD can run in two modes, and the Robust MCP Server works with both:

Feature	Headless Mode	GUI Mode
Object creation	Yes	Yes
Boolean operations	Yes	Yes
Export (STEP, STL, etc.)	Yes	Yes
Save documents	Yes	Yes
Screenshots	No	Yes
Object colors	No	Yes
Object visibility	No	Yes
Camera control	No	Yes
Interactive selection	No	Yes

Starting FreeCAD

GUI Mode (for interactive work with visual feedback):

# Using just commands (from source)
just freecad::run-gui

# Or start FreeCAD normally and click "Start Bridge" in the workbench

Headless Mode (for automation, CI/CD, or when you don't need visual feedback):

# Using just commands (from source)
just freecad::run-headless

# Or run directly with FreeCADCmd
FreeCADCmd ~/.local/share/FreeCAD/Mod/FreecadRobustMCPBridge/freecad_mcp_bridge/blocking_bridge.py

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Next Steps

• Quick Start - Create your first model with AI assistance
• Connection Modes - Detailed guide on different connection modes