CAD MCP Server

AI-native CAD inspection, no CAD license required. CAD MCP Server bundles a WebAssembly Open CASCADE kernel so LLM tools can read, measure, and compare STEP files locally. The server returns measured facts; your AI assistant interprets engineering meaning.

Quick Start

npx -y cad-mcp-server

Add this to your MCP client config (Claude Desktop, OpenCode, Cursor, etc.):

{
  "mcpServers": {
    "cad": {
      "command": "npx",
      "args": ["-y", "cad-mcp-server"]
    }
  }
}

Point the AI at any STEP or STP file on your local filesystem.

Use Cases

| Who | What they ask | |---|---| | Mechanical lead | "Review this STEP file like a mechanical lead before release. What are the top design or manufacturing risks?" | | Manufacturing engineer | "Build a first-pass CNC plan: likely setups, drilling directions, and cost-driving features." | | QC engineer | "Create an inspection plan from the STEP file. What should we measure? What's missing?" | | Procurement / sourcing | "Prepare an RFQ summary: part count, envelope, complexity drivers, and questions the supplier will ask." | | Design engineer (revision) | "Compare Rev A and Rev B as an ECO review. What changed? What should be rechecked?" | | Hobbyist / maker | "Can these parts fit on a 200 x 200 x 300 mm printer? What needs splitting or reorientation?" |

MCP Tools

| Tool | Purpose | |---|---| | inspect_step_file | Fast first-pass overview: validity, size, bodies, topology counts, metadata. | | find_step_faces | Search B-rep faces by surface type, area, normal, body, grouping, and sort. | | find_step_edges | Search B-rep edges by curve type, length, radius, body, grouping, and sort. | | get_step_entities | Retrieve known face or edge IDs with requested fields. | | query_step_pmi | Query lightweight PMI/GD&T, dimensions, datums, and annotations. | | compare_step_files | Compare two STEP files by whole-model geometry, topology, and metadata. |

Recommended workflow: inspect first, drill into groups or summaries, ask for specific entity IDs, then request adjacency or exact fields only where needed.

How It Works

STEP files are parsed locally by a stripped Open CASCADE Technology (OCCT) kernel compiled to WebAssembly. No data leaves your machine. No Docker, no cloud API, no CAD vendor dependency. The package bundles everything — just npx and go.

Why CAD MCP Server?

• Zero install friction. One npx command, no native CAD software, no licenses.
• Read-only by design. The server measures geometry; the AI interprets meaning. No risk of accidental edits.
• Local-first. All processing stays on your machine. STEP files never leave your filesystem.
• WASM-speed. OCCT runs at near-native speed in a bundled WebAssembly kernel.
• LLM-native output. Results are structured JSON designed for AI consumption, not human eyeballs.

What It Is Not

• Not a CAD editor — no geometry creation or modification.
• Not a CAM system — no toolpath generation.
• Not a manufacturability certifier — it provides evidence, not conclusions.
• Not an AP242 PMI engine — PMI hints are lightweight and heuristic-based.
• Not a feature-tree recovery tool — STEP is a boundary-representation format.

Good AI answers separate measured facts, assumptions, and recommendations.

Roadmap

• v0.2 — Advanced face adjacency graphs, edge-vexity classification, larger file support.
• v0.3 — Assembly hierarchy traversal, color/layer metadata, improved PMI coverage.
• v1.0 — Stable tool surface, first-semver API guarantees.

Interested in hosted or enterprise features? Let us know via GitHub Discussions.

Requirements

• Node.js 22 or newer
• Local access to STEP/STP files

No Docker, Open CASCADE install, or native CAD application required.

Distribution

The npm package includes:

• MCP server JavaScript in dist/
• Bundled occt-wasm package with optimized occt-wasm.wasm geometry kernel
• TypeScript declarations for published runtime files

Contributing

Contributions welcome. See CONTRIBUTING.md for development setup, testing, and pull request guidelines.

License

This project is MIT licensed — free for all uses, commercial included.

The bundled occt-wasm backend uses Open CASCADE Technology (LGPL-2.1). Review the third-party notices before redistributing modified kernel builds.

Support

If CAD MCP Server saves you time, consider sponsoring development.