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 (recommended)
      • 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

Resource	Description
Documentation	Full documentation, guides, and API reference
Docker Hub	Pre-built Docker images for easy deployment
PyPI	Python package for pip installation
GitHub Releases	Release archives and changelogs

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 (recommended)

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)

Note: The containerized Robust MCP Server only supports xmlrpc and socket modes since FreeCAD runs on your host machine (not in the container). The container connects to FreeCAD via host.docker.internal.

Configuration

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

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)

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:

{
  "mcpServers": {
    "freecad": {
      "command": "docker",
      "args": [
        "run", "--rm", "-i",
        "--add-host=host.docker.internal:host-gateway",
        "-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
• --add-host=host.docker.internal:host-gateway allows the container to connect to FreeCAD on your host (Linux only; macOS/Windows have this built-in)
• FREECAD_SOCKET_HOST=host.docker.internal tells the Robust MCP Server to connect to FreeCAD on your host machine

Usage

Starting the MCP Bridge in FreeCAD

Before your AI assistant can connect, you need to start the MCP bridge inside FreeCAD:

Option A: Using the Workbench (Recommended)

1. Install the Robust MCP Bridge workbench via FreeCAD's Addon Manager:

   • Edit -> Preferences -> Addon Manager
   • Search for "Robust MCP Bridge"
   • Install and restart FreeCAD

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:

   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:

1. Open FreeCAD
2. Go to Edit -> Preferences -> Addon Manager
3. Find "Robust MCP Bridge" in the list
4. Click Uninstall
5. 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)

Tool	Description	Mode
execute_python	Execute arbitrary Python code in FreeCAD's context	All
get_freecad_version	Get FreeCAD version, build date, and Python version	All
get_connection_status	Check MCP bridge connection status and latency	All
get_console_output	Get recent FreeCAD console output (up to N lines)	All
get_mcp_server_environment	Get Robust MCP Server environment (OS, hostname, instance_id)	All

Document Management (7 tools)

Tool	Description	Mode
list_documents	List all open documents with metadata	All
get_active_document	Get information about the active document	All
create_document	Create a new FreeCAD document	All
open_document	Open an existing .FCStd file	All
save_document	Save a document to disk	All
close_document	Close a document (with optional save)	All
recompute_document	Force recomputation of all objects	All

Object Creation - Primitives (8 tools)

Tool	Description	Mode
create_object	Create a generic FreeCAD object by type ID	All
create_box	Create a Part::Box with length, width, height	All
create_cylinder	Create a Part::Cylinder with radius, height, angle	All
create_sphere	Create a Part::Sphere with radius	All
create_cone	Create a Part::Cone with two radii and height	All
create_torus	Create a Part::Torus (donut) with radii and angles	All
create_wedge	Create a Part::Wedge (tapered box)	All
create_helix	Create a Part::Helix curve for sweeps and threads	All

Object Management (12 tools)

Tool	Description	Mode
list_objects	List all objects in a document	All
inspect_object	Get detailed object info (properties, shape, etc.)	All
edit_object	Modify properties of an existing object	All
delete_object	Delete an object from a document	All
set_placement	Set object position and rotation	All
scale_object	Scale an object uniformly or non-uniformly	All
rotate_object	Rotate an object around an axis	All
copy_object	Create a copy of an object	All
mirror_object	Mirror an object across a plane (XY, XZ, YZ)	All
boolean_operation	Fuse, cut, or intersect objects	All
get_selection	Get currently selected objects	GUI
set_selection	Select specific objects by name	GUI
clear_selection	Clear all selections	GUI

PartDesign - Sketching (14 tools)

Tool	Description	Mode
create_partdesign_body	Create a PartDesign::Body container	All
create_sketch	Create a sketch on a plane or face	All
add_sketch_rectangle	Add a rectangle to a sketch	All
add_sketch_circle	Add a circle to a sketch	All
add_sketch_line	Add a line (with optional construction flag)	All
add_sketch_arc	Add an arc by center, radius, and angles	All
add_sketch_point	Add a point (useful for hole centers)	All
pad_sketch	Extrude a sketch (additive)	All
pocket_sketch	Cut into solid using a sketch (subtractive)	All
revolution_sketch	Revolve a sketch around an axis (additive)	All
groove_sketch	Revolve a sketch around an axis (subtractive)	All
create_hole	Create parametric holes with optional threading	All
loft_sketches	Create a loft through multiple sketches	All
sweep_sketch	Sweep a profile along a spine path	All

PartDesign - Patterns & Edges (5 tools)

Tool	Description	Mode
linear_pattern	Create linear pattern of a feature	All
polar_pattern	Create polar/circular pattern of a feature	All
mirrored_feature	Mirror a feature across a plane	All
fillet_edges	Add fillets (rounded edges)	All
chamfer_edges	Add chamfers (beveled edges)	All

View & Display (11 tools)

Tool	Description	Mode
get_screenshot	Capture a screenshot of the 3D view	GUI
set_view_angle	Set camera to standard views (Front, Top, etc.)	GUI
fit_all	Zoom to fit all objects in view	GUI
zoom_in	Zoom in by a factor	GUI
zoom_out	Zoom out by a factor	GUI
set_camera_position	Set camera position and look-at point	GUI
set_object_visibility	Show/hide objects	GUI
set_display_mode	Set display mode (Shaded, Wireframe, etc.)	GUI
set_object_color	Set object color as RGB values	GUI
list_workbenches	List available FreeCAD workbenches	All
activate_workbench	Switch to a different workbench	All

Undo/Redo (3 tools)

Tool	Description	Mode
undo	Undo the last operation	All
redo	Redo a previously undone operation	All
get_undo_redo_status	Get available undo/redo operations	All

Export/Import (7 tools)

Tool	Description	Mode
export_step	Export to STEP format (ISO CAD exchange)	All
export_stl	Export to STL format (3D printing)	All
export_3mf	Export to 3MF format (modern 3D printing)	All
export_obj	Export to OBJ format (Wavefront)	All
export_iges	Export to IGES format (older CAD exchange)	All
import_step	Import a STEP file	All
import_stl	Import an STL file as mesh	All

Macro Management (6 tools)

Tool	Description	Mode
list_macros	List all available FreeCAD macros	All
run_macro	Execute a macro by name	All
create_macro	Create a new macro file	All
read_macro	Read macro source code	All
delete_macro	Delete a user macro	All
create_macro_from_template	Create macro from template (basic, part, etc.)	All

Parts Library (2 tools)

Tool	Description	Mode
list_parts_library	List parts in FreeCAD's parts library	All
insert_part_from_library	Insert a part from the library	All

---

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:

Placeholder	Description	Example
/path/to/mise/shims/uv	Full path to uv via mise shims	~/.local/share/mise/shims/uv
/path/to/freecad-addon-robust-mcp-server	Project directory	/home/me/dev/freecad-addon-robust-mcp-server
/path/to/mise/shims	mise shims directory for PATH	~/.local/share/mise/shims

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.

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License

MIT License - see LICENSE for details.