CAD MCP servers: a practical guide and comparison

Hosted build123d with five tools: get_cad_guide (how to write a parametric model, with 3D-printing defaults), list_designs, get_design, run_model (runs the script and returns errors, per-part checks and pictures) and save_design (saves a version and returns a link where you move sliders and download STL, 3MF or STEP). Your AI subscription does the thinking; we run the CAD. It is built for parts you will print: the model gets the same 3D printing rules and fastener tables as our own designer, and your measured printer fit if you saved one.

Limits: you need a free account, one run at a time, 300 runs per day. It does not drive Fusion, FreeCAD or any desktop CAD. Full setup on the BuildCAD AI MCP page.

claude mcp add --transport http buildcad-ai https://buildcad.ai/api/mcp

{
  "mcpServers": {
    "buildcad-ai": { "url": "https://buildcad.ai/api/mcp" }
  }
}

The most complete local build123d server: renders, measurements, hole finding, a printability check and an export gate that refuses invalid solids. Its README reports that on the CADGenBench benchmark (June 2026) it raised the same model's score from 0.360 to 0.457. A good choice if you want everything on your machine and are happy with Python and uv.

{
  "mcpServers": {
    "build123d-mcp": {
      "command": "uv",
      "args": ["tool", "run", "--python", "3.12", "build123d-mcp@latest"]
    }
  }
}

Its README places the config in ~/.claude/mcp.json for Claude Code; Claude Code reads ~/.claude.json and .mcp.json, so use claude mcp add instead.

A Python CAD library on the SMLib NURBS kernel, from the company behind ClassCAD, with an MCP server built in. Its snapshot tool is strong on visual checks: technical drawings, sections, x-ray, zebra stripes and before and after pixel diffs. Also a Claude Code plugin.

claude mcp add smlibpy --scope user -- uvx --from "smlibpy[mcp]" smlibpy-mcp

The ClassCAD engine as WebAssembly, driven from Node, with snapshots and mass properties. Free for private use and evaluation after a one-time sign-in to a free classcad.ch account; STEP export and commercial use need a paid tier. Its docs recommend the Claude Code plugin over claude mcp add.

claude plugin marketplace add awv-informatik/classcad-ai
claude plugin install classcad@classcad

{
  "mcpServers": {
    "classcad": { "command": "npx", "args": ["-y", "@classcad/mcp@latest"] }
  }
}

The most starred CAD MCP server for an open-source CAD app. Install the add-on into FreeCAD 1.0 or 1.1, start its RPC server from the add-on, then add the server to your client. Most tools can return a screenshot of the FreeCAD view, and it can run FEM analysis with CalculiX. Older alternatives (bonninr/freecad_mcp, contextform/freecad-mcp) have not been updated since 2025.

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

Built into Fusion desktop since May 2026. Turn it on in Preferences > General > API > “Fusion MCP Server (runs locally on this device)”. In Claude Desktop, add Autodesk Fusion from Settings > Connectors > Browse connectors (Autodesk's docs say not to add it as a custom connector). Other clients use the local URL. Autodesk's own caveat: not yet reliable for complex models or full assemblies. Community alternatives: fusion360-mcp-server (93 tools including STEP and STL export, interference checks and view sheets; marked beta).

{
  "mcpServers": {
    "autodesk-fusion": { "url": "http://127.0.0.1:27182/mcp" }
  }
}

PTC's official server, in early access through Onshape Labs since August 2026. It writes FeatureScript (Onshape's language for custom features), checks the errors and inspects the geometry, rather than modelling parts feature by feature. Subscribe in the Onshape App Store, then sign in from your client.

claude mcp add --transport http onshape https://fs-mcp.labs.onshape.app/mcp

For general modelling in Onshape, community servers call the Onshape REST API with your API keys (from dev-portal.onshape.com). jarvis-onshape-mcp, built on hedless/onshape-mcp, adds shaded multi-view pictures and per-feature size and mass changes so the model can see what each feature did, and installs as a Claude Code plugin.

Renders, sections, measurements (including watertightness and printability) and interference checks for OpenSCAD scripts. OpenSCAD makes meshes, so there is no STEP; for simple printable parts that is often fine. Needs OpenSCAD installed.

claude mcp add openscad --transport stdio -- uvx openscad-mcp

The most starred server on this page by far, for Blender scenes and meshes: modelling, materials, and pictures from any angle. It is not a precision CAD tool (no exact solids or STEP), but it is the right one for organic shapes, scenes and renders. The package was renamed from blender-mcp to mcp-for-blender.

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