Freecad Addon Robust MCP Server README

FreeCAD Robust MCP Server

An MCP (Model Context Protocol) server that enables integration between AI assistants (Claude, GPT, and other MCP-compatible tools) and FreeCAD, allowing AI-assisted development and debugging of 3D models, macros, and workbenches.

Table of Contents

• FreeCAD Robust MCP Server
  • Table of Contents
  • Features
  • Installation Requirements / Dependencies
  • For Users
    • Quick Links
  • Robust MCP Server
    • Installation
      • Using pip
      • Using mise and just (from source)
      • Using Docker
    • Configuration
      • Environment Variables
      • Connection Modes
      • MCP Client Configuration
    • Usage
      • Starting the MCP Bridge in FreeCAD
        • Option A: Using the Workbench (Recommended)
        • Option B: Using just commands (from source)
      • Uninstalling the MCP Bridge
        • Checking for Legacy Components
        • Manual Cleanup (if needed)
      • Running Modes
        • XML-RPC Mode (Recommended)
        • Socket Mode (JSON-RPC)
        • Headless Mode
        • Embedded Mode (Linux Only)
    • Available Tools
      • Execution & Debugging (5 tools)
      • Document Management (7 tools)
      • Object Creation - Primitives (8 tools)
      • Object Management (12 tools)
      • PartDesign - Sketching (14 tools)
      • PartDesign - Patterns & Edges (5 tools)
      • View & Display (11 tools)
      • Undo/Redo (3 tools)
      • Export/Import (7 tools)
      • Macro Management (6 tools)
      • Parts Library (2 tools)
  • For Developers
  • Robust MCP Server Development
    • Prerequisites
    • Initial Setup
    • MCP Client Configuration (Development)
    • Development Workflow
    • Running FreeCAD with the MCP Bridge
      • GUI Mode (recommended for development)
      • Headless Mode (for automation/CI)
    • Running Tests
    • Code Quality
  • Architecture
  • Acknowledgements
    • Related Projects
  • License

The macros that were originally in this repo under the /macros directory have been permanently moved to two new GitHub repos:

• spkane/freecad-macro-cut-for-magnets
• spkane/freecad-macro-3d-print-multi-export

FreeCAD Forum: addon discussion post

Features

• 150+ MCP Tools: Comprehensive CAD operations including primitives, PartDesign, booleans, export
• Multiple Connection Modes: XML-RPC (recommended), JSON-RPC socket, or embedded
• GUI & Headless Support: Full modeling in headless mode, plus screenshots/colors in GUI mode
• Macro Development: Create, edit, run, and template FreeCAD macros via MCP

Installation Requirements / Dependencies

• FreeCAD 0.21+ or 1.0+
• Python 3.11 (required for FreeCAD ABI compatibility)

For Users

This section covers installation and usage for end users who want to use the Robust MCP Server with AI assistants.

Quick Links

Robust MCP Server

Note: The Linux container and PyPI package are both named freecad-robust-mcp which differs slightly from this git repository name.

Installation

Using pip

pip install freecad-robust-mcp

Using mise and just (from source)

git clone https://github.com/spkane/freecad-addon-robust-mcp-server.git
cd freecad-addon-robust-mcp-server

# Install mise via the Official mise installer script (if not already installed)
curl https://mise.run | sh

mise trust
mise install
just setup

Using Docker

Run the Robust MCP Server in a container. This is useful for isolated environments or when you don't want to install Python dependencies on your host.

# Pull from Docker Hub (when published)
docker pull spkane/freecad-robust-mcp

# Or build locally
git clone https://github.com/spkane/freecad-addon-robust-mcp-server.git
cd freecad-addon-robust-mcp-server
docker build -t freecad-robust-mcp .

# Or use just commands (if you have mise/just installed)
just docker::build        # Build for local architecture
just docker::build-multi  # Build multi-arch (amd64 + arm64)

The containerized Robust MCP Server only supports xmlrpc and socket modes because FreeCAD runs on the host. This topology currently works only with Docker Desktop, whose host.docker.internal forwarding can reach a host-loopback listener.

The container also needs the existing bridge pairing credential; pairing the host account does not provision it in the container. A portable secure provisioning procedure has not yet been validated, so run the MCP server on the host unless the container credential is already provisioned securely.

Security and Linux limitation: The FreeCAD bridge listens on loopback and requires pairing before accepting Python execution. Docker Engine on Linux maps host.docker.internal or host-gateway to a bridge-network address, which cannot reach that loopback listener. Run the MCP server directly on the Linux host instead. Do not expose ports 9875 or 9876 by rebinding the bridge to 0.0.0.0; protected remote transport is not implemented yet.

Configuration

Environment Variables

Connection Modes

Note: Embedded mode crashes on macOS because FreeCAD's FreeCAD.so links to @rpath/libpython3.11.dylib, which conflicts with external Python interpreters. Use xmlrpc or socket mode on macOS and Windows.

MCP Client Configuration

Add something like the following to your MCP client settings. For Claude Code, this is ~/.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-addon-robust-mcp-server", "freecad-mcp"],
      "env": {
        "FREECAD_MODE": "xmlrpc"
      }
    }
  }
}

If using Docker Desktop on macOS or Windows:

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

Docker configuration notes:

• --rm removes the container after it exits
• -i keeps stdin open for MCP communication
• FREECAD_SOCKET_HOST=host.docker.internal tells the Robust MCP Server to connect to FreeCAD on your host machine

This example is not supported on Docker Engine for Linux. Its host gateway cannot reach the bridge's loopback-only listener. FREECAD_SOCKET_HOST changes only the address dialed by the MCP server; it does not change the address on which the FreeCAD bridge listens.

Usage

Starting the MCP Bridge in FreeCAD

Before starting the bridge, pair the MCP server and FreeCAD bridge using the same operating-system user account:

freecad-mcp --pair-bridge

For a source checkout use uv run freecad-mcp --pair-bridge. For container or different-account setups, see the pairing instructions. Use matching server and workbench builds that support pairing; the published 0.6.x releases predate it. Until a pairing-capable release is published, use the server and workbench from the same current source checkout as described in the installation guide.

Then start the MCP bridge inside FreeCAD:

Option A: Using the Workbench (Recommended)

1. Install the workbench using the installation guide. The workbench is not currently in the public Addon Manager catalog.

2. Start the bridge:

   • Switch to the Robust MCP Bridge workbench
   • Click the Start MCP Bridge button in the toolbar
   • Or use the menu: MCP Bridge -> Start Bridge

3. You should see in the FreeCAD console:

   textCopy

   MCP Bridge started!
     - XML-RPC: localhost:9875
     - Socket: localhost:9876
   

Option B: Using just commands (from source)

# Start FreeCAD with MCP bridge auto-started
just freecad::run-gui

# Or for headless/automation mode:
just freecad::run-headless

After starting the bridge, start/restart your MCP client (Claude Code, etc.) - it will connect automatically

Uninstalling the MCP Bridge

To uninstall the Robust MCP Bridge workbench:

For a source installation, run just install::uninstall-mcp-bridge-workbench from the checkout, then restart FreeCAD. The command selects the latest profile at uninstall time. If the workbench was installed in another profile, remove its package directory from that original profile’s Mod directory instead. For a release archive, remove its extracted package directory from the original profile’s Mod directory and restart FreeCAD.

Checking for Legacy Components

If you previously used older versions of this project, you may have legacy components installed. Run this command to check what's installed and get cleanup instructions:

just install::status

Manual Cleanup (if needed)

Remove any legacy files that may conflict with the workbench:

# macOS - remove legacy plugin and macro
rm -rf ~/Library/Application\ Support/FreeCAD/Mod/MCPBridge/
rm -f ~/Library/Application\ Support/FreeCAD/Macro/StartMCPBridge.FCMacro

# Linux - remove legacy plugin and macro
rm -rf ~/.local/share/FreeCAD/Mod/MCPBridge/
rm -f ~/.local/share/FreeCAD/Macro/StartMCPBridge.FCMacro

Running Modes

XML-RPC Mode (Recommended)

Connects to a running FreeCAD instance via XML-RPC. Works on all platforms.

FREECAD_MODE=xmlrpc freecad-mcp

Socket Mode (JSON-RPC)

Connects via JSON-RPC socket. Works on all platforms.

FREECAD_MODE=socket freecad-mcp

Headless Mode

Run FreeCAD in console mode without GUI. Useful for automation.

# If installed from source:
just freecad::run-headless

Note: Screenshot and view features are not available in headless mode.

Embedded Mode (Linux Only)

Runs FreeCAD in-process. Only works on Linux - crashes on macOS/Windows.

FREECAD_MODE=embedded freecad-mcp

Available Tools

The Robust MCP Server provides 150+ tools organized into categories. Tools marked with GUI require FreeCAD to be running in GUI mode; they will return an error in headless mode.

Execution & Debugging (5 tools)

Document Management (7 tools)

Object Creation - Primitives (8 tools)

Object Management (12 tools)

PartDesign - Sketching (14 tools)

PartDesign - Patterns & Edges (5 tools)

View & Display (11 tools)

Undo/Redo (3 tools)

Export/Import (7 tools)

Macro Management (6 tools)

Parts Library (2 tools)

For Developers

This section covers development setup, contributing, and working with the codebase.

Robust MCP Server Development

Prerequisites

• mise - Tool version manager
• FreeCAD 0.21+ or 1.0+

Initial Setup

# Clone the repository
git clone https://github.com/spkane/freecad-addon-robust-mcp-server.git
cd freecad-addon-robust-mcp-server

# Install mise via the Official mise installer script (if not already installed)
curl https://mise.run | sh

# Install all tools (Python 3.11, uv, just, pre-commit)
mise trust
mise install

# Set up the development environment
just setup

This installs:

• Python 3.11 - Required for FreeCAD ABI compatibility
• uv - Fast Python package manager
• just - Command runner for development workflows
• pre-commit - Git hooks for code quality

MCP Client Configuration (Development)

Create a .mcp.json file in the project directory:

{
  "mcpServers": {
    "freecad": {
      "command": "/path/to/mise/shims/uv",
      "args": ["run", "--project", "/path/to/freecad-addon-robust-mcp-server", "freecad-mcp"],
      "env": {
        "FREECAD_MODE": "xmlrpc",
        "FREECAD_SOCKET_HOST": "localhost",
        "FREECAD_XMLRPC_PORT": "9875",
        "PATH": "/path/to/mise/shims:/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin"
      }
    }
  }
}

Replace the paths with your actual paths:

Finding your mise shims path:

mise where uv | sed 's|/installs/.*|/shims|'
# Example: /home/user/.local/share/mise/shims (on Linux) or ~/.local/share/mise/shims (on macOS)

Development Workflow

Commands are organized into modules. Use just to see top-level commands, or just list-<module> to see module-specific commands.

# Show top-level commands and available modules
just

# Show commands in a specific module
just list-mcp           # Robust MCP Server commands
just list-freecad       # FreeCAD plugin/macro commands
just list-install       # Installation commands
just list-quality       # Code quality commands
just list-testing       # Test commands
just list-docker        # Docker commands
just list-documentation # Documentation commands
just list-dev           # Development utilities

# List ALL commands from all modules
just list-all

# Install/update dependencies
just install::mcp-server

# Run all checks (linting, type checking, tests)
just all

# Quality commands
just quality::lint       # Run ruff linter
just quality::typecheck  # Run mypy type checker
just quality::format     # Format code
just quality::check      # Run all pre-commit hooks

# Testing commands
just testing::unit       # Run unit tests
just testing::cov        # Run tests with coverage
just testing::integration # Run integration tests

# Run the Robust MCP Server (or with debug logging)
just mcp::run
just mcp::run-debug

# Docker commands
just docker::build        # Build image for local architecture
just docker::build-multi  # Build multi-arch image (amd64 + arm64)
just docker::run          # Run container

Running FreeCAD with the MCP Bridge

GUI Mode (recommended for development)

# Start FreeCAD with auto-started bridge
just freecad::run-gui

Headless Mode (for automation/CI)

just freecad::run-headless

Running Tests

# Unit tests only (no FreeCAD required)
just testing::unit

# Unit tests with coverage
just testing::cov

# Integration tests (requires running FreeCAD bridge)
just testing::integration

# Integration tests with automatic FreeCAD startup
just testing::integration-auto

Code Quality

The project uses strict code quality checks via pre-commit:

• Ruff - Linting and formatting
• MyPy - Type checking
• Bandit - Security scanning
• Codespell - Spell checking
• Secrets scanning - Gitleaks, detect-secrets, TruffleHog

# Run all pre-commit hooks
just quality::check

# Run security/secrets scans
just quality::security
just quality::secrets

Architecture

See the detailed architecture document for design documentation covering:

• Module structure
• Bridge communication protocols
• Tool registration patterns
• FreeCAD plugin architecture

Acknowledgements

This project was developed after analyzing several existing FreeCAD Robust MCP implementations. We are grateful to these projects for their pioneering work and the ideas they contributed to the FreeCAD + AI ecosystem:

Related Projects

• neka-nat/freecad-mcp (MIT License) - The queue-based thread safety pattern and XML-RPC protocol design (port 9875) were directly inspired by this project. Our implementation maintains protocol compatibility while being a complete rewrite with additional features.

• jango-blockchained/mcp-freecad - Inspired our connection recovery mechanisms and multi-mode architecture approach.

• contextform/freecad-mcp - Informed our comprehensive PartDesign and Part workbench tool coverage.

• ATOI-Ming/FreeCAD-MCP - Inspired our macro development toolkit including templates, validation, and automatic imports.

• bonninr/freecad_mcp - Influenced our simple socket-based communication approach.

See docs/COMPARISON.md for a detailed analysis of these implementations and the design decisions they informed.

License

Code is distributed under Apache License 2.0; previously MIT-licensed contributions retain their original MIT terms. Workbench icons use CC BY-NC-SA 4.0. See NOTICE for attribution.