OpenSCAD MCP Server

A local MCP server that turns OpenSCAD source or explicit primitive dimensions into editable SCAD, STL geometry, and four PNG previews. The connected assistant can write SCAD for complex designs; this server compiles and renders it with the installed OpenSCAD executable.

Status: the supported implementation is in src/openscad_mcp. The previous image generation, CUDA reconstruction, remote processing, and printer code is archived in legacy/. It is unfinished and is not part of the installed server. See the audit and machine test results.

Install

Requires Python 3.11+ and OpenSCAD. No API keys, CUDA, Open3D, or separate image renderer are required.

Install OpenSCAD using the official downloads. On macOS, the current native Apple Silicon/Intel build is available with:

brew install --cask openscad@snapshot
openscad --version

On Debian/Ubuntu, sudo apt-get install openscad installs the distribution package. Linux PNG rendering may need an X display; use xvfb-run -a around the server or tests on a headless machine. Windows users can set OPENSCAD_EXECUTABLE to the full path of openscad.exe.

git clone https://github.com/jhacksman/OpenSCAD-MCP-Server.git
cd OpenSCAD-MCP-Server
uv sync --locked
uv run openscad-mcp --help

Alternatively, install into a virtual environment with python -m pip install . and run openscad-mcp. requirements.txt installs this same package. uv.lock pins the tested dependency resolution; the project metadata permits compatible updates.

On an external filesystem that cannot create symlinks, put the environment on the internal disk:

export UV_PROJECT_ENVIRONMENT="$HOME/.cache/openscad-mcp-venv"
uv sync --locked

Docker and Jetson

A headless stdio image is available through the root Dockerfile. See Docker setup and verification for build commands, MCP client configuration, persistent model storage, and Glama listing requirements. The image needs no GPU.

For the hardware question in issue #19, see Jetson Orin Nano and CUDA. The supported server does not use CUDA; the archived reconstruction prototype is not restored by this Docker support.

Connect an MCP client

Stdio is the default. Configure the client to launch the server process, using absolute paths:

{
  "mcpServers": {
    "openscad": {
      "command": "/absolute/path/to/venv/bin/openscad-mcp",
      "args": ["--output-dir", "/absolute/path/to/models"]
    }
  }
}

For clients supporting Streamable HTTP:

uv run openscad-mcp --transport http --port 8000

The MCP endpoint is http://127.0.0.1:8000/mcp. / is server information; /health reports the OpenSCAD version and primitive defaults. HTTP also serves preview pages and downloads. In stdio mode, use returned absolute file paths or get_model_preview; there is no HTTP listener.

Tools

Example arguments to create_3d_model:

{
  "model_type": "box",
  "parameters": {"width": 40, "depth": 30, "height": 20, "thickness": 2}
}

Dimensions are in millimeters. Supported types: cube (also rectangular blocks), sphere, cylinder, box (open hollow box), rounded_box (solid), tube, cone, torus, prism (right triangular cross-section), hexagonal_prism, and text. Call get_capabilities for each type's exact parameter names. A torus uses the radius to the tube center (major_radius) and the tube radius (minor_radius).

The optional description parser recognizes named dimensions such as hollow box width 40 mm depth 30 mm height 20 mm thickness 2 mm or cube 2 cm wide 1 inch high. It supports mm, cm, m, and inches; omitted units mean mm. It is a small parser, not a general natural-language model. Unspecified dimensions use the returned defaults. Prefer explicit parameters for precision. For arbitrary objects, have the assistant write self-contained SCAD and call create_model_from_scad.

{
  "scad_code": "difference() { cube([40,30,8]); translate([20,15,-1]) cylinder(h=10,r=5,$fn=48); }",
  "description": "Mounting plate with a through hole"
}

To modify a primitive:

{"model_id": "ID_FROM_CREATION", "parameters": {"height": 25}}

For custom models, call get_model_source with the model ID to retrieve scad_code and revision directly through MCP. Edit the returned source, then call modify_3d_model with the new scad_code and expected_revision set to the revision you read. No access to the server's filesystem is needed to read the source.

The same optional revision check works for primitive parameter edits:

{
  "model_id": "ID_FROM_CREATION",
  "parameters": {"height": 25},
  "expected_revision": "REVISION_FROM_GET_MODEL"
}

If another edit has already committed, the operation fails before rendering or changing files. MCP reports a tool error; the HTTP /tool_call API returns 409 with current_revision. Read the latest source/parameters and incorporate the intervening changes before retrying. Omitting expected_revision preserves the original unconditional edit behavior.

Only SCAD retains editable source parameters. CSG is an evaluated geometry tree. STL and 3MF are meshes; they do not preserve the design's parametric relationships. AMF (removed in current OpenSCAD builds), STEP, OBJ, 2D exports, image reconstruction, and printing are not offered.

HTTP smoke test

With the HTTP server running:

curl --fail http://127.0.0.1:8000/tool_call \
  -H 'Content-Type: application/json' \
  -d '{"tool_name":"create_3d_model","tool_params":{"model_type":"box","parameters":{"width":40,"depth":30,"height":20,"thickness":2}}}'

Open the returned preview_url on the same server. Download /download/MODEL_ID?format=stl or ?format=scad. /tool_call is a convenience JSON API, separate from the actual MCP protocol at /mcp. Image retrieval over this API uses /preview/VIEW/MODEL_ID.

Behavior and limits

• Creation succeeds only after a real STL and all four PNGs have been generated. Renderer failures, empty output, and OpenSCAD warnings/errors are reported as failures; no placeholder geometry or preview is substituted.
• Edits create a new revision and update the manifest only after successful rendering. Earlier revisions remain on disk. Models survive server restarts.
• Default storage is ~/.local/share/openscad-mcp/models. Override with --output-dir or OPENSCAD_OUTPUT_DIR. Each render subprocess has a 120-second timeout, configurable with --timeout. A model requires five subprocesses, so the total request can take longer.
• Run one server process per output directory. Renders and edits are serialized. There is no automatic disk cleanup, distributed job queue, or multi-process store coordination.
• This is a trusted local tool. Custom SCAD executes with the current user's file access, including OpenSCAD import, include, and use; it is not sandboxed. HTTP binds to loopback and rejects non-local Host/Origin headers. There is no authentication or supported public/LAN deployment.
• Tested locally on macOS arm64 and in Ubuntu 24.04 CI under Xvfb. Windows and other platform/display combinations are unverified. No hardware printer or remote GPU was exercised.

Development and verification

uv sync --locked --group dev
uv run ruff check src/openscad_mcp tests scripts
uv run ruff format --check src/openscad_mcp tests scripts
uv run pytest -q

The full suite requires OpenSCAD and fails if it is unavailable. Tests launch real stdio and HTTP server processes, use the official MCP client, download exports, decode PNGs, inspect mesh topology/dimensions/volume, test persistence and failed edits, and exercise invalid requests. uv run pytest -m 'not integration' runs the unit checks only and does not establish end-to-end correctness.

License

MIT, copyright 2026 Jack Hacksman.