FreeCAD MCP

This repository is a FreeCAD MCP that allows you to control FreeCAD from Claude Desktop.

Demo

Design a flange

Design a toy car

Design a part from 2D drawing

Input 2D drawing

Demo

This is the conversation history. https://claude.ai/share/7b48fd60-68ba-46fb-bb21-2fbb17399b48

Install addon

FreeCAD Addon directory is

• Windows: %APPDATA%\FreeCAD\Mod\
• Mac:
  • FreeCAD 1.1: ~/Library/Application\ Support/FreeCAD/v1-1/Mod/
  • FreeCAD 1.0: ~/Library/Application\ Support/FreeCAD/v1-0/Mod/
• Linux:
  • Ubuntu: ~/.FreeCAD/Mod/ or ~/snap/freecad/common/Mod/ (if you install FreeCAD from snap)
  • Debian: ~/.local/share/FreeCAD/Mod
  • Arch / CachyOS (FreeCAD 1.1 from extra/freecad): ~/.local/share/FreeCAD/v1-1/Mod/
  • Flatpak: ~/.var/app/org.freecad.FreeCAD/data/FreeCAD/v1-1/Mod/

Please put addon/FreeCADMCP directory to the addon directory.

git clone https://github.com/neka-nat/freecad-mcp.git
cd freecad-mcp

# For Linux (Ubuntu/Debian)
mkdir -p ~/.FreeCAD/Mod/
cp -r addon/FreeCADMCP ~/.FreeCAD/Mod/

# For Linux (Arch/CachyOS, FreeCAD 1.1 from extra/freecad)
mkdir -p ~/.local/share/FreeCAD/v1-1/Mod/
cp -r addon/FreeCADMCP ~/.local/share/FreeCAD/v1-1/Mod/

# For Linux (Flatpak)
mkdir -p ~/.var/app/org.freecad.FreeCAD/data/FreeCAD/v1-1/Mod/
cp -r addon/FreeCADMCP ~/.var/app/org.freecad.FreeCAD/data/FreeCAD/v1-1/Mod/

# For macOS (FreeCAD 1.1)
mkdir -p ~/Library/Application\ Support/FreeCAD/v1-1/Mod/
cp -r addon/FreeCADMCP ~/Library/Application\ Support/FreeCAD/v1-1/Mod/

When you install addon, you need to restart FreeCAD. You can select "MCP Addon" from Workbench list and use it.

And you can start RPC server by "Start RPC Server" command in "FreeCAD MCP" toolbar.

Auto-Start RPC Server

By default, the RPC server must be started manually each time FreeCAD opens. To start it automatically:

1. Open the FreeCAD MCP menu (switch to the MCP Addon workbench first)
2. Check Auto-Start Server

The setting is saved to freecad_mcp_settings.json and persists across sessions. On the next FreeCAD launch, the RPC server will start automatically once the application finishes loading.

You can disable it at any time by unchecking Auto-Start Server in the same menu.

Setting up Claude Desktop

Pre-installation of the uvx is required.

And you need to edit Claude Desktop config file, claude_desktop_config.json.

For user.

{
  "mcpServers": {
    "freecad": {
      "command": "uvx",
      "args": [
        "freecad-mcp"
      ]
    }
  }
}

If you want to save token, you can set only_text_feedback to true and use only text feedback.

{
  "mcpServers": {
    "freecad": {
      "command": "uvx",
      "args": [
        "freecad-mcp",
        "--only-text-feedback"
      ]
    }
  }
}

Screenshots can also be controlled per tool call instead of globally: every tool that returns a screenshot accepts an optional include_screenshot parameter (pass false to get text-only feedback, e.g. for analytical scripts or intermediate steps) and an optional view_name parameter to orient the screenshot ("Isometric" by default, or "Front", "Top", "Right", etc.). The --only-text-feedback flag always wins: when it is set, no screenshots are returned regardless of include_screenshot.

For developer. First, you need clone this repository.

git clone https://github.com/neka-nat/freecad-mcp.git

{
  "mcpServers": {
    "freecad": {
      "command": "uv",
      "args": [
        "--directory",
        "/path/to/freecad-mcp/",
        "run",
        "freecad-mcp"
      ]
    }
  }
}

Remote Connections

By default the RPC server does not accept remote connections and listens on localhost. To control FreeCAD from another machine on your network:

1. Enable remote connections in FreeCAD

In the FreeCAD MCP toolbar:

1. Check Remote Connections — the RPC server will bind to 0.0.0.0 (all interfaces) on the next restart. For security reasons, it only accepts connections from the IP addresses or CIDR subnets specified in the Allowed IPs field. By default this is 127.0.0.1.

2. Click Configure Allowed IPs and enter a comma-separated list of IP addresses or CIDR subnets that are allowed to connect, e.g.:

   192.168.1.100, 10.0.0.0/24
   

   127.0.0.1 is always the default. Invalid entries are rejected with an error dialog. Restart the RPC server after changing these settings.

2. Point the MCP server at the remote host

Pass the --host flag with the IP address or hostname of the machine running FreeCAD:

{
  "mcpServers": {
    "freecad": {
      "command": "uvx",
      "args": [
        "freecad-mcp",
        "--host", "192.168.1.100"
      ]
    }
  }
}

The --host value is validated on startup — it must be a valid IPv4/IPv6 address or hostname.

Tools

• create_document: Create a new document in FreeCAD.
• create_object: Create a new object in FreeCAD.
• edit_object: Edit an object in FreeCAD.
• delete_object: Delete an object in FreeCAD.
• execute_code: Execute arbitrary Python code in FreeCAD.
• execute_code_headless: Run a FreeCAD script in a separate freecadcmd process (crash-safe for heavy OCCT work such as helical threads, lofts, big booleans); returns exit status and output. Pair with reload_document.
• insert_part_from_library: Insert a part from the parts library.
• get_view: Get a screenshot of the active view.
• get_objects: Get all objects in a document.
• get_object: Get an object in a document.
• get_parts_list: Get the list of parts in the parts library.
• get_rpc_status: Report RPC and GUI-dispatch health without using the FreeCAD GUI thread.
• get_async_status: Report background jobs started by execute_code_async (state and error traceback) without using the GUI thread.
• run_fem_analysis: Run the CalculiX solver on an existing Fem::FemAnalysis and return summary results (max von Mises stress, max displacement, node count, working directory). Auto-creates a SolverCcxTools if the analysis has none. See examples/cantilever_fem.py for an end-to-end usage example.

Tools that return a screenshot (create_object, edit_object, delete_object, execute_code, insert_part_from_library, get_objects, get_object, run_fem_analysis) accept optional include_screenshot (default true) and view_name (default "Isometric") parameters to suppress or reorient the returned image per call.

GUI dispatch timeouts

GUI calls have separate queue and execution budgets. The queue budget defaults to the execution budget; a call cancelled before it starts will not run later. execute_code allows 90 seconds in the queue and 90 seconds after GUI execution starts. The bundled client's socket timeout covers both plus a 30-second margin (210 seconds total). FEM calls use the requested timeout for each budget, with a client socket timeout of at least 2 * timeout + 30 seconds. Other clients and MCP hosts must allow these response times in their own timeout settings.

GUI-thread operations run one at a time in FIFO order. An operation's timeout counts from the moment it starts on the GUI thread, not from when it was queued: a call that arrives while another operation is still running waits for its turn without spending its own budget. The wait itself is bounded by a separate queue timeout (defaults to the same value); when it expires the task is dropped before it starts without marking dispatch as stuck. Concurrent execute_code calls are therefore safe to issue, but they still execute sequentially, so total wall time is the sum of the individual runs.

If a GUI-thread operation exceeds its timeout after it has started, the bridge returns GUI_DISPATCH_STUCK and rejects later GUI operations immediately. Calls that were already queued keep waiting (up to their queue timeout) and run once the stuck operation returns. Use get_rpc_status from a separate RPC client to identify the operation that is still running. The RPC server handles connections concurrently, so diagnostics do not wait for another request to finish. Document queries (get_object, get_objects, and list_documents) run on the GUI thread alongside modelling operations and report an RPC fault if dispatch times out or is stuck. FreeCAD GUI work cannot be force-cancelled safely; if the status does not return to healthy after the operation finishes, restart FreeCAD.

execute_code and execute_code_async share a persistent script namespace with FreeCAD/App and FreeCADGui/Gui aliases. Script variables survive between calls without overwriting the RPC server's own functions. This prevents accidental name collisions; code execution still has FreeCAD's full privileges.

Async code must keep document and view access on the GUI thread. Build independent OCCT shapes in the worker, then use commit(fn, timeout=120) to apply the result and recompute the document on the GUI thread. The helper returns fn's value or raises RuntimeError on failure. It persists in the shared namespace so saved functions can reuse it in later async calls; calling it from execute_code or inside a GUI callback raises immediately. Concurrent scripts share live variables and must coordinate any intentional writes to the same data.

After an execute_code exception on a FreeCAD development build, inspect any new FeaturePython object before mutating or deleting it. In particular, do not continue with an object whose required Proxy was never installed, as touching that broken object can wedge FreeCAD's GUI thread.

Headless execution

execute_code_headless writes the script to a file and runs it with freecadcmd -c in a separate process. Use it for OpenCascade work that may segfault or block the GUI for minutes: makeHelix + makePipeShell threads, lofts and sweeps, booleans with many B-spline tools. A native crash only ends the helper process; the tool reports the signal (e.g. SIGSEGV) together with everything the script printed, and the GUI keeps its documents. The script must open and save documents itself (FreeCAD.openDocument, doc.save(), Shape.exportBrep); afterwards reload_document refreshes the GUI copy.

The executable runs on the machine hosting the MCP server; --host only selects the GUI RPC host. Use file paths accessible on the MCP server machine. The timeout must be positive and finite. A timeout returns partial stdout/stderr, and temporary scripts are removed on success, failure, and timeout.

The executable is auto-detected (freecadcmd or Snap's freecad.cmd on PATH, then the org.freecad.FreeCAD Flatpak). Override with freecad-mcp --freecadcmd "flatpak run --command=freecadcmd org.freecad.FreeCAD".

Background jobs

execute_code_async returns a job_id. get_async_status(job_id) reports whether the job is running, done or failed, and for failed jobs the exception and traceback that previously reached only FreeCAD's Report View. All running jobs and the 20 most recently completed jobs are retained in memory until FreeCAD exits. get_async_status() lists this history; get_rpc_status lists the ids of jobs still running. Job status does not wait for GUI cleanup. Scripts still use commit() for document access, and script success does not certify geometry validity. Install the updated addon to use job status; with an older addon, continue polling a document status object and checking Report View.

Contributors

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