Onshape MCP Server

Enhanced Model Context Protocol (MCP) server for programmatic CAD modeling with Onshape.

Features

This MCP server provides comprehensive programmatic access to Onshape's REST API, enabling:

Core Capabilities (45 tools)

• Document Discovery - Search and list projects, find Part Studios, navigate workspaces

• Parametric Sketches - Rectangles, circles, lines, and arcs on standard planes

• Feature Management - Extrude, revolve, thicken, fillet, chamfer, boolean, and pattern features

• Assembly Management - Create assemblies, add instances, position parts, create mates (fastened, slider, revolute, cylindrical)

• Assembly Analysis - Interference checking, position verification, face coordinate systems, body details

• Variable Tables - Read and write Onshape variable tables for parametric designs

• FeatureScript - Evaluate FeatureScript expressions, get bounding boxes

• Export - Export Part Studios and Assemblies to STL, STEP, PARASOLID, GLTF, OBJ

• Part Studio Management - Create and manage Part Studios programmatically

Installation

Prerequisites

• Python 3.10 or higher

• Onshape account with API access

• Onshape API keys (access key and secret key)

Setup

1. Clone the repository:

git clone https://github.com/hedless/onshape-mcp.git
cd onshape-mcp

2. Create a virtual environment:

python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

3. Install dependencies:

pip install -e .

4. Set up environment variables:

export ONSHAPE_ACCESS_KEY="your_access_key"
export ONSHAPE_SECRET_KEY="your_secret_key"

Or create a .env file:

ONSHAPE_ACCESS_KEY=your_access_key
ONSHAPE_SECRET_KEY=your_secret_key

Getting Onshape API Keys

1. Go to Onshape Developer Portal

2. Sign in with your Onshape account

3. Create a new API key

4. Copy the Access Key and Secret Key

Usage

Running the Server

onshape-mcp

Or directly with Python:

python -m onshape_mcp.server

Configuring with Claude Code

Add to your ~/.claude/mcp.json:

{
  "mcpServers": {
    "onshape": {
      "command": "/absolute/path/to/onshape-mcp/venv/bin/python",
      "args": ["-m", "onshape_mcp.server"],
      "env": {
        "ONSHAPE_ACCESS_KEY": "your_access_key_here",
        "ONSHAPE_SECRET_KEY": "your_secret_key_here"
      }
    }
  }
}

Important Notes:

• Use the absolute path to your virtual environment's Python executable

• Find your path: cd onshape-mcp && pwd to get the directory path

• On Windows: Use C:/path/to/onshape-mcp/venv/Scripts/python.exe

• Replace the API keys with your actual keys from Onshape Developer Portal

• Restart Claude Code after editing mcp.json

Verify it works: Ask Claude Code: "Can you list my Onshape documents?"

For complete setup instructions, see docs/QUICK_START.md.

Available Tools

Document & Navigation Tools

Assembly Tools

Assembly Analysis Tools

Sketch Tools

All sketch tools support plane (Front/Top/Right) and name parameters. Dimensions are in inches.

Feature Tools

Variable & Feature Tools

FeatureScript Tools

Export Tools

Architecture

onshape_mcp/
├── api/
│   ├── client.py         # HTTP client with HMAC authentication
│   ├── documents.py      # Document discovery & navigation
│   ├── partstudio.py     # Part Studio management
│   ├── variables.py      # Variable table management
│   ├── assemblies.py     # Assembly lifecycle, mates & features
│   ├── export.py         # Part Studio & Assembly export
│   └── featurescript.py  # FeatureScript evaluation
├── builders/
│   ├── sketch.py         # Sketch builder (rectangle, circle, line, arc, polygon)
│   ├── extrude.py        # Extrude feature builder
│   ├── revolve.py        # Revolve feature builder
│   ├── fillet.py         # Fillet feature builder
│   ├── chamfer.py        # Chamfer feature builder
│   ├── boolean.py        # Boolean operations (union, subtract, intersect)
│   ├── pattern.py        # Linear & circular pattern builders
│   ├── mate.py           # Mate connector & mate builders (face-based)
│   └── thicken.py        # Thicken feature builder
├── analysis/
│   ├── interference.py   # Bounding-box interference detection
│   ├── positioning.py    # Instance position queries & alignment
│   └── face_cs.py        # Face coordinate system queries
├── tools/
│   └── __init__.py       # MCP tool definitions
└── server.py             # Main MCP server (45 tools)

Examples

Example 1: Finding and Working on a Project

# Search for your project
documents = await search_documents(query="robot arm", limit=5)

# Get the first matching document
doc_id = documents[0].id

# Get comprehensive summary
summary = await get_document_summary(doc_id)

# Find Part Studios in main workspace
workspace_id = summary['workspaces'][0].id
part_studios = await find_part_studios(doc_id, workspace_id, namePattern="base")

# Now work with the Part Studio
elem_id = part_studios[0].id

Example 2: Creating a Parametric Cabinet

# Set variables
await set_variable(doc_id, ws_id, elem_id, "width", "39.5 in")
await set_variable(doc_id, ws_id, elem_id, "depth", "16 in")
await set_variable(doc_id, ws_id, elem_id, "height", "67.125 in")
await set_variable(doc_id, ws_id, elem_id, "wall_thickness", "0.75 in")

# Create side panel sketch
await create_sketch_rectangle(
    doc_id, ws_id, elem_id,
    name="Side Panel",
    plane="Front",
    corner1=[0, 0],
    corner2=[16, 67.125],
    variableWidth="depth",
    variableHeight="height"
)

# Extrude to create side
await create_extrude(
    doc_id, ws_id, elem_id,
    name="Side Extrude",
    sketchFeatureId="<sketch_id>",
    depth=0.75,
    variableDepth="wall_thickness"
)

Development

Running Tests

The project has comprehensive test coverage with 471 unit tests.

# Run all tests
pytest

# Run with coverage
pytest --cov

# Run specific module tests
pytest tests/api/test_documents.py -v

# Use make commands
make test
make test-cov
make coverage-html

For detailed testing documentation, see docs/TESTING.md.

Code Formatting

ruff format .
ruff check .

Documentation

Getting Started

• docs/QUICK_START.md - Quick start guide for Claude Code users

• docs/DEV_SETUP.md - Development environment setup with SSE mode and debugging

Development & Testing

• docs/TESTING.md - Testing guide and best practices

• docs/TEST_SUMMARY.md - Test suite overview

• docs/FEATURE_SUMMARY.md - Implementation details and statistics

API & Implementation

• docs/ONSHAPE_API_IMPROVEMENTS.md - API format fixes and BTMSketch-151 implementation

• docs/SKETCH_PLANE_REFERENCE_GUIDE.md - Advanced: Geometry-referenced sketch planes

• docs/NEXT_STEPS_GEOMETRY_REFERENCES.md - Roadmap for geometry reference implementation

• docs/DOCUMENT_DISCOVERY.md - Complete guide to document discovery features

• docs/PARTS_ASSEMBLY_TOOLS.md - Parts and assembly tool documentation

Project Analysis & Research

• docs/CARPENTRY_PRINCIPLES_FOR_CAD.md - How to think like a carpenter in CAD

• docs/LEARNING_SUMMARY.md - Summary of side panel analysis and learnings

• docs/DISPLAY_CABINETS_ANALYSIS_SUMMARY.md - Analysis of display cabinets project

• docs/AGENT_CREATION_GUIDE.md - Guide for creating CAD agents

• docs/CREATING_CAD_EXPERT_AGENT.md - Creating specialized CAD expert agents

Knowledge Base & Examples

• knowledge_base/assembly_workflow_guide.md - Comprehensive assembly methodology (positioning, mates, solver behavior)

• examples/cabinet_assembly.md - Complete worked example: cabinet with sliding drawers

• knowledge_base/ - Onshape feature examples and research

Roadmap

Current Status

• Document discovery and navigation (10 tools)

• Sketch creation with rectangles, circles, lines, and arcs

• Feature tools: extrude, revolve, thicken, fillet, chamfer, boolean, patterns

• Full assembly management: fastened, slider, revolute, and cylindrical mates with face-based mate connectors

• Assembly analysis: interference checking, position verification, face coordinate systems

• Variable table management

• FeatureScript evaluation and bounding box queries

• Export to STL, STEP, PARASOLID, GLTF, OBJ

• 471 comprehensive unit tests

• Live-tested on multi-part assemblies (25-instance cabinet with 66 features)

In Research

• Geometry-referenced sketch planes - Create sketches on faces from existing features (see docs/SKETCH_PLANE_REFERENCE_GUIDE.md)

• Query API investigation - How to programmatically reference geometry

• Entity ID mapping - Understanding Onshape's internal ID system

Near-Term Priorities

• Implement create_sketch_on_geometry() for carpentry-correct cabinet assembly

• Sketch constraints (coincident, parallel, tangent, etc.)

• Pocket cuts and profiles for joinery (dados, rabbets)

Long-Term Goals

• Drawing creation

• Bill of Materials (BOM) generation

• Advanced constraints and relations

• Configuration parameter support

Woodworking-Specific Features

• Joinery library (dado, rabbet, mortise & tenon, dovetail)

• Standard hardware patterns (shelf pins, drawer slides)

• Cut list generation

• Material optimization (sheet layout)

• Assembly instructions generation

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License

Acknowledgments

• Inspired by OnPy

• Built on the Model Context Protocol

• Onshape API documentation: https://onshape-public.github.io/docs/

Support

For issues and questions:

• GitHub Issues: https://github.com/hedless/onshape-mcp/issues

• Onshape API Forum: https://forum.onshape.com/