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

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 1.0.2 or newer is required. FreeCAD 1.1.4

• Python 3.11 or newer for the external server; embedded mode requires a Python

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

For the everyday setup, see the Quick Start for the server, workbench, pairing, and assistant configuration. Install or update both components to compatible versions; pairing requires 0.7.0 or later.

Using pip

pip install freecad-robust-mcp

Using GitHub release assets

Download the server wheel and matching workbench archive for your chosen release. The release asset installation guide covers installation, updates, FreeCAD profiles, and release candidates. Install and update both components; cam-gate-v1.json is not needed for installation.

Using uv (from source)

Install Git and uv first.

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

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

| 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 | Default execution timeout in ms (1000-600000) | 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 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

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. Install compatible server and workbench releases at version 0.7.0 or later; 0.6.x releases predate pairing. For development, use both components from the same 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.

1. Start the bridge:

1. 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:

On Linux or macOS, run just install::uninstall-mcp-bridge-workbench from the checkout to remove a source installation. The command selects the latest profile; pass the original profile's Mod directory if it differs. On Windows, remove the RobustMCPBridge directory from the original profile's Mod directory. For a release archive, remove its extracted package directory from the original profile's Mod directory. Restart FreeCAD afterward.

##### 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)

Check each FreeCAD profile you use for legacy MCPBridge workbench folders and StartMCPBridge.FCMacro macro files. Move obsolete copies out of the profile after confirming they are no longer needed. Profile paths vary by FreeCAD version; see the installation guide for how to find the active user data directory.

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 1.1.4 or newer is recommended for security.

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- 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.

License

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