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

Tool	Description
list_documents	List documents with filtering and sorting
search_documents	Search documents by name or description
get_document	Get detailed document information
get_document_summary	Get comprehensive summary with workspaces and elements
find_part_studios	Find Part Studios with optional name filtering
get_elements	Get all elements (Part Studios, Assemblies, BOMs) in a workspace
get_parts	Get all parts from a Part Studio
create_document	Create a new Onshape document
create_part_studio	Create a new Part Studio in a document

Assembly Tools

Tool	Description
create_assembly	Create a new Assembly in a document
add_assembly_instance	Add a part or sub-assembly instance to an assembly
get_assembly	Get assembly structure with instances and occurrences
transform_instance	Apply a relative transform (inches/degrees). Fails on fixed instances.
set_instance_position	Set absolute position (resets rotation). Fails on fixed instances.
align_instance_to_face	Align one instance flush against a face of another
create_mate_connector	Create an explicit mate connector on a face with offsets
create_fastened_mate	Create a rigid (fastened) mate between two instances
create_slider_mate	Create a linear motion mate. First instance slides relative to second.
create_revolute_mate	Create a rotational mate. First instance rotates relative to second.
create_cylindrical_mate	Create a slide+rotate mate. First instance moves relative to second.
delete_feature	Delete a feature (mate, mate connector, etc.) from an assembly or Part Studio

Assembly Analysis Tools

Tool	Description
get_assembly_positions	Get positions, sizes, and bounds of all instances (in inches)
get_assembly_features	Get all features with their state (OK/ERROR/SUPPRESSED)
get_body_details	Get face IDs, surface types, normals, and origins for all parts
get_face_coordinate_system	Query the outward-facing coordinate system for a specific face
check_assembly_interference	Check for overlapping/interfering parts using bounding box detection

Sketch Tools

Tool	Description
create_sketch_rectangle	Rectangle with optional variable references for width/height
create_sketch_circle	Circle with center point and radius
create_sketch_line	Line from start point to end point
create_sketch_arc	Arc with center, radius, start angle, and end angle

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

Feature Tools

Tool	Description
create_extrude	Extrude a sketch with depth, optional variable reference, and operation type
create_thicken	Thicken a sketch into a solid with optional midplane/opposite direction
create_revolve	Revolve a sketch around an axis (X/Y/Z) with angle and operation type
create_fillet	Round edges by edge IDs with radius (supports variable references)
create_chamfer	Bevel edges by edge IDs with distance (supports variable references)
create_linear_pattern	Repeat features along an axis (X/Y/Z) with distance and count
create_circular_pattern	Repeat features around an axis with count and angle spread
create_boolean	Union, subtract, or intersect bodies by deterministic IDs

Variable & Feature Tools

Tool	Description
get_variables	Get all variables from a Part Studio variable table
set_variable	Set or update a variable (e.g., "0.75 in")
get_features	Get all features from a Part Studio

FeatureScript Tools

Tool	Description
eval_featurescript	Evaluate a FeatureScript lambda expression (read-only)
get_bounding_box	Get the tight bounding box of all parts in a Part Studio

Export Tools

Tool	Description
export_part_studio	Export to STL, STEP, PARASOLID, GLTF, or OBJ (optional partId filter)
export_assembly	Export to STL, STEP, or GLTF

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/