civil3d-mcp Non-Official from Autodesk. Only research

AI-powered Autodesk Civil 3D automation via FastMCP (Python 3.11).
Connects Claude directly to a running Civil 3D instance using COM automation — no companion plugin required.

How it works

Claude Desktop  ──stdio──►  FastMCP server (Python 3.11)
                               │
                               ├── win32com.client.GetActiveObject("AutoCAD.Application")
                               │       │
                               └── pythonnet clr → AeccDbMgd.dll / AeccLandMgd.dll
                                       │
                                       ▼
                               Civil 3D (acad.exe, running on same machine)

Python talks directly to the running Civil 3D process via the Windows COM server that Civil 3D registers automatically when it starts. pythonnet additionally loads Autodesk's .NET managed assemblies to access Civil 3D–specific objects (surfaces, alignments, COGO points) that aren't exposed through the base AutoCAD COM interface.

Architecture

See ARCHITECTURE.md for the full system design: layer breakdown, COM connection strategy, request lifecycle, threading model, COM out-parameter handling, error strategy, and the Civil 3D object model reference.

Requirements

Installation

# 1. Clone
git clone https://github.com/yourname/civil3d-mcp-python
cd civil3d-mcp-python

# 2. Install dependencies (Windows, Python 3.11)
pip install -r requirements.txt

# 3. Install the package in editable mode
pip install -e .

# 4. Run the pre-flight environment checker
python setup_check.py
# Use --fix to auto-install any missing pip packages:
python setup_check.py --fix

# 5. (Optional) copy environment config
copy .env.example .env
# Edit .env if Civil 3D is not in the default installation path

Configuration

Claude Desktop

Edit %APPDATA%\Claude\claude_desktop_config.json and add:

{
  "mcpServers": {
    "civil3d-mcp": {
      "command": "civil3d-mcp"
    }
  }
}

Or, if you prefer to run without installing the package:

{
  "mcpServers": {
    "civil3d-mcp": {
      "command": "python",
      "args": ["-m", "civil3d_mcp.server"],
      "cwd": "C:\\path\\to\\civil3d-mcp-python",
      "env": {
        "PYTHONPATH": "C:\\path\\to\\civil3d-mcp-python\\src",
        "CIVIL3D_BIN_PATH": "C:\\Program Files\\Autodesk\\AutoCAD 2026"
      }
    }
  }
}

Restart Claude Desktop. The hammer icon (🔨) in the toolbar confirms the server is connected.

Environment variables

Available tools (19 total)

Drawing

COGO Points

Lines & Polylines

Surfaces

Alignments & Profiles

Corridors

Example prompts

"What surfaces are in this drawing and what are their elevation ranges?"

"Create a COGO point at northing 1000, easting 500, elevation 12.5 with description 'BM-01'"

"What is the elevation of the EG surface at easting 45200, northing 87300?"

"List all alignments and give me the geometry breakdown of CL-MAIN"

"What is the station and offset of point (45300, 87450) relative to alignment CL-MAIN?"

"Create a polyline on layer BOUNDARY with vertices at (0,0,0), (100,0,0), (100,100,0), (0,100,0) and close it"

Project structure

civil3d-mcp-python/
├── src/
│   └── civil3d_mcp/
│       ├── __init__.py           # Public API: Civil3DClient, Civil3DError
│       ├── server.py             # FastMCP app, lifecycle, tool registration
│       ├── client.py             # Civil3DClient — all COM/pythonnet calls
│       ├── tools_drawing.py      # Tools 1-3:  drawing info
│       ├── tools_cogo.py         # Tools 4-6:  COGO points
│       ├── tools_lines.py        # Tools 7-9:  lines & polylines
│       ├── tools_surfaces.py     # Tools 10-13: surfaces
│       ├── tools_alignments.py  # Tools 14-18: alignments & profiles
│       └── tools_corridors.py   # Tool  19:    corridors
├── tests/
│   ├── __init__.py
│   └── test_tools.py             # pytest suite (fully mocked COM)
├── setup.py                      # Legacy setuptools entry point
├── setup_check.py                # Pre-flight environment checker
├── pyproject.toml                # PEP 517/518 build config
├── requirements.txt              # Runtime dependencies
├── requirements-dev.txt          # Dev/test dependencies
├── conftest.py                   # pytest sys.path injection
├── .env.example                  # Environment variable template
├── claude_desktop_config_snippet.json
├── ARCHITECTURE.md               # Full system design documentation
└── README.md

Running tests

pip install -e ".[dev]"
pytest tests/ -v

Tests use a fully mocked Civil3DClient — no Civil 3D installation required to run the test suite.

Troubleshooting

"Could not connect to a running Civil 3D instance"
→ Make sure Civil 3D is open and a drawing is loaded before starting the MCP server.

"Civil 3D .NET assemblies not found"
→ Set CIVIL3D_BIN_PATH in .env to the folder containing AeccDbMgd.dll
→ Default path: C:\Program Files\Autodesk\AutoCAD 2024

"Surfaces / Alignments collection not accessible"
→ Ensure you launched Civil 3D (not plain AutoCAD). The server falls back to AutoCAD's ProgID if the Civil 3D ProgID isn't registered.

Hammer icon not showing in Claude Desktop
→ Check Claude Desktop logs: %APPDATA%\Claude\logs\
→ Run python -m civil3d_mcp.server manually to see startup errors.

License

MIT