loki-cad-mcp — CAD & 3D Modelling MCP Server

Give AI assistants real CAD superpowers — create, edit, validate, and export 3D models without opening SolidWorks, Fusion 360, or Blender.

What It Does

Ask Claude:

"Create an M6 bolt, fillet all edges by 0.5 mm, export to STL, then validate it for FDM printing."

And it just works — no GUI, no scripts, pure conversation.

11 MCP Tools

| Tool | Description | |------|-------------| | cad_create_model | Create box, cylinder, sphere, cone, or torus from parameters | | cad_export_model | Export to STL, STEP, OBJ, GLTF, DXF, or SVG | | cad_query_properties | Volume, surface area, bounding box, centre of mass, optional mass | | cad_apply_operation | Fillet, chamfer, shell, extrude, revolve, boolean ops, mirror, pattern | | cad_validate_model | 3D printability check — watertight, manifold, wall thickness | | cad_list_templates | Browse mechanical / architectural / organic template library | | cad_load_template | Instantiate a template with custom parameters | | cad_import_file | Import an existing STL / STEP / OBJ into memory | | cad_sketch_2d | Create 2D sketches (line, arc, circle, rect) on any plane | | cad_translate_model | Move a model by (x, y, z) offset in mm | | cad_repair_mesh | Fix STL mesh for 3D printing — winding, normals, holes |

Where Are My Files Saved?

Every model you export (STL, STEP, OBJ, etc.) lands in a folder you control. Set CAD_MCP_MODELS_DIR in your config to a real folder on your machine — this is the most important setting.

| Platform | Recommended value | |----------|------------------| | Windows | C:/Users/YourName/Documents/cad-models | | macOS | /Users/yourname/Documents/cad-models | | Linux | /home/yourname/cad-models |

Why does this matter for npx? Without CAD_MCP_MODELS_DIR, files are saved inside the npx cache (~/.npm/_npx/<hash>/node_modules/loki-cad-mcp/models/exports/) — buried and hard to find. Always set this variable.

The folder is created automatically if it doesn't exist. Inside it you'll find:

cad-models/
├── exports/   ← your STL, STEP, OBJ, GLTF, DXF, SVG files
└── previews/  ← PNG preview images

Installation

Prerequisites

| Requirement | Notes | |-------------|-------| | Node.js ≥ 18 | nodejs.org | | Python 3.9–3.12 | cadquery-ocp has no wheels for 3.13+ |

Option 1 — npx (nothing to install)

No global install needed — npx downloads and runs the package on demand.

npx -y loki-cad-mcp

Option 2 — Global npm install

npm install -g loki-cad-mcp

Then reference loki-cad-mcp as the command in your config.

Option 3 — Clone & build

git clone https://github.com/PRATHVI9607/CAD_Autodesk_MCP.git
cd CAD_Autodesk_MCP
npm install          # builds dist/ automatically

Python setup (required for all options)

CadQuery must be installed in a Python 3.9–3.12 environment. Run the setup script once — it creates a .venv and installs all dependencies:

# macOS / Linux
bash scripts/setup.sh

# Windows PowerShell
.\scripts\setup.ps1

Or manually:

python3.12 -m venv .venv
source .venv/bin/activate          # macOS/Linux
# .venv\Scripts\activate           # Windows
pip install -r python/requirements.txt

Configure Claude Desktop

This is how you wire up the server — you never run npx manually. Claude Desktop reads this config file and launches the server automatically.

Step 1 — Open your config file

| Platform | Path | |----------|------| | Windows | %APPDATA%\Claude\claude_desktop_config.json | | macOS | ~/Library/Application Support/Claude/claude_desktop_config.json | | Linux | ~/.config/Claude/claude_desktop_config.json |

Open it in any text editor (Notepad, VS Code, etc.). If it doesn't exist yet, create it.

Step 2 — Paste the config for your platform

Windows — npx

{
  "mcpServers": {
    "loki-cad-mcp": {
      "command": "npx",
      "args": ["-y", "loki-cad-mcp"],
      "env": {
        "CAD_MCP_MODELS_DIR": "C:/Users/YourName/Documents/cad-models",
        "CAD_MCP_PYTHON_CMD": "python"
      }
    }
  }
}

macOS — npx

{
  "mcpServers": {
    "loki-cad-mcp": {
      "command": "npx",
      "args": ["-y", "loki-cad-mcp"],
      "env": {
        "CAD_MCP_MODELS_DIR": "/Users/yourname/Documents/cad-models",
        "CAD_MCP_PYTHON_CMD": "python3"
      }
    }
  }
}

Linux — npx

{
  "mcpServers": {
    "loki-cad-mcp": {
      "command": "npx",
      "args": ["-y", "loki-cad-mcp"],
      "env": {
        "CAD_MCP_MODELS_DIR": "/home/yourname/cad-models",
        "CAD_MCP_PYTHON_CMD": "python3"
      }
    }
  }
}

Replace YourName / yourname with your actual username. The folder (cad-models) is created automatically — you do not need to make it yourself.

Step 3 — Restart Claude Desktop

Close and reopen Claude Desktop. The server starts automatically on the first tool call.

Your exported files will appear at:

• Windows: C:\Users\YourName\Documents\cad-models\exports\
• macOS/Linux: ~/Documents/cad-models/exports/

Cloned repo config (if you cloned instead of using npx)

Windows

{
  "mcpServers": {
    "loki-cad-mcp": {
      "command": "node",
      "args": ["C:/path/to/CAD_Autodesk_MCP/dist/index.js"],
      "env": {
        "CAD_MCP_MODELS_DIR": "C:/Users/YourName/Documents/cad-models",
        "CAD_MCP_PYTHON_CMD": "C:/path/to/CAD_Autodesk_MCP/.venv/Scripts/python.exe"
      }
    }
  }
}

macOS / Linux

{
  "mcpServers": {
    "loki-cad-mcp": {
      "command": "node",
      "args": ["/path/to/CAD_Autodesk_MCP/dist/index.js"],
      "env": {
        "CAD_MCP_MODELS_DIR": "/Users/yourname/Documents/cad-models",
        "CAD_MCP_PYTHON_CMD": "/path/to/CAD_Autodesk_MCP/.venv/bin/python"
      }
    }
  }
}

Environment Variables

| Variable | Default | Description | |----------|---------|-------------| | CAD_MCP_MODELS_DIR | ./models ⚠️ | Set this to an absolute path. Default buries files in the npx cache when using npx. | | CAD_MCP_PYTHON_CMD | auto-detected | Path to Python 3.9–3.12 executable. Auto-detects .venv first, then system python3/python. | | CAD_MCP_LOGS_DIR | ./logs | Server log file directory. | | CAD_MCP_GEOMETRY_TIMEOUT_MS | 30000 | Geometry operation timeout in ms. | | CAD_MCP_RENDER_TIMEOUT_MS | 60000 | Render/preview timeout in ms. |

Architecture

MCP Client (Claude Desktop / Claude Code / Cursor / etc.)
    │  stdio transport — MCP protocol (JSON-RPC 2.0)
    ▼
dist/index.js              — 11 tools, Zod validation, StdioServerTransport
dist/http-server.js        — optional REST wrapper on port 3000 (testing)
    │  JSON-RPC 2.0 over subprocess stdin/stdout
    ▼
python/cadquery_server.py  — persistent geometry server
    ├─ CadQuery / OpenCASCADE  (parametric BRep modelling)
    ├─ trimesh                 (mesh validation, repair, OBJ/GLTF export)
    └─ validators.py           (3D-printability checks)
    ▼
CAD_MCP_MODELS_DIR/exports/    (STL, STEP, OBJ, GLTF, DXF, SVG)
CAD_MCP_MODELS_DIR/previews/   (PNG previews)

Development

# Clone & install
git clone https://github.com/PRATHVI9607/CAD_Autodesk_MCP.git
cd cad-mcp
npm install

# Set up Python
.\scripts\setup.ps1   # Windows
bash scripts/setup.sh # macOS/Linux

# Type-check
npm run typecheck

# Build
npm run build

# Start HTTP test server (port 3000)
npm run start:http

# Run integration tests
npm run test:http

Security

• All output files are strictly confined to CAD_MCP_MODELS_DIR — path traversal is rejected
• Model names validated against /^[A-Za-z0-9_\-]{1,128}$/
• Negative / zero dimensions are rejected before reaching the CAD kernel
• Geometry operations time out after 30 s; renders after 60 s
• Python executable path validated against shell-injection characters
• No raw Python stack traces exposed to MCP clients
• HTTP test server binds to localhost only — do not expose to a network

Templates

9 parametric templates ready to use:

| Category | Templates | |----------|-----------| | Mechanical | bolt_m6, nut_m6, bracket_l, gear_spur | | Architectural | wall_section, column_round, slab_flat | | Organic | blob_sphere, ring_torus |

# In Claude:
"Load the bolt_m6 template with shank_length=40 and export to STL."

License

MIT — see LICENSE.