GOLEM-3DMCP

"Shaped from clay, brought to life by words"

The most powerful MCP server for Rhinoceros 3D — 105 tools giving AI full read/write access to Rhino 8.

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GOLEM-3DMCP implements the Model Context Protocol to give AI agents direct, programmatic control of Rhino 8 — create geometry, run booleans, drive Grasshopper, capture viewports, and execute arbitrary Python scripts, all through natural language.

Works with Claude Code, Cursor, Windsurf, and any MCP-compatible host.

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Demo — A City Built Entirely by AI

An entire city generated in Rhino 8 through GOLEM-3DMCP — roads, skyscrapers, houses, trees, people, vehicles, a stadium, bridge, ferris wheel, harbor, wind turbines, and a floating GOLEM hologram. All created by Claude Code using natural language commands.

Watch the full demo on YouTube

Full city overview — ground, roads, buildings, park, harbor, sky

Skyline view — skyscrapers, bridge, wind turbines, floating GOLEM hologram

Close-up — GOLEM monument plaza, residential buildings, fountain

Street level — vehicles, people, street lamps, stadium, harbor with boats

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Install

pip install golem-3dmcp

That's it. Three commands to go from zero to AI-powered Rhino:

# 1. Install
pip install golem-3dmcp

# 2. Deploy the Rhino plugin (one-time)
golem install-rhino

# 3. Verify everything works
golem doctor

Connect to Your AI Agent

Add to your MCP configuration (Claude Code, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "golem-3dmcp": {
      "command": "uvx",
      "args": ["golem-3dmcp"]
    }
  }
}

Start talking to Rhino through AI.

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105 Tools Across 9 Categories

Category	Tools	Highlights
Scene Intelligence	10	Document info, layers, objects, groups, blocks — full pagination
Geometry Creation	38	Points, curves, NURBS, solids, mesh, SubD, text, dimensions, hatches
Geometry Operations	19	Boolean union/difference/intersection, trim, split, offset, fillet, chamfer
Surface Operations	12	Loft, sweep1/2, revolve, extrude, network surface, patch, edge surface, unroll
Object Manipulation	21	Move, copy, rotate, scale, mirror, array, join, explode, group, properties
Grasshopper	9	Open definitions, set/get parameters, recompute, bake, inspect components
Viewport & Visualization	13	Capture screenshots (base64 PNG), camera control, named views, display modes
File Operations	9	Save, open, import, export (STL, OBJ, STEP, IGES, FBX, 3MF, DWG, PDF...)
Script Execution	4	Execute arbitrary Python with full RhinoCommon access, run Rhino commands

See Tool Reference for the complete API with parameters and examples.

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Architecture

 AI Agent (Claude Code / Cursor / Windsurf)
      |
      |  MCP (stdio, JSON-RPC)
      v
+---------------------------+
|     GOLEM MCP Server      |
|     Python 3.10+          |
|     FastMCP + 9 tool      |
|     modules               |
+---------------------------+
      |
      |  TCP 127.0.0.1:9876
      |  Length-prefixed JSON
      v
+---------------------------+
|     Rhino Plugin          |
|     Python 3.9 (embedded) |
|     TCP Server            |
|     9 handler modules     |
+---------------------------+
      |
      |  RhinoCommon + rhinoscriptsyntax
      v
+---------------------------+       +-------------------------+
|     Rhinoceros 3D         | <---> |   Grasshopper           |
|     Document, Geometry,   |       |   Sub-server :9877      |
|     Layers, Views         |       |   Definitions, Params   |
+---------------------------+       +-------------------------+

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Quick Start Examples

Create and combine geometry:

Create a 100 x 50 x 30 box on a layer called 'Structure',
then boolean-union it with a sphere of radius 20 centred at [50, 25, 30].

Query the scene:

List all objects on the 'Walls' layer and tell me their volumes.

Drive Grasshopper:

Open parametric_facade.gh, set the 'PanelCount' slider to 24,
recompute, and bake the result to a 'Facade' layer.

Capture a viewport:

Set perspective view to shaded mode, zoom to extents, and capture a screenshot.

Execute arbitrary Python:

import Rhino.Geometry as rg
pts = [rg.Point3d(i*10, 0, i**2) for i in range(20)]
crv = rg.Curve.CreateInterpolatedCurve(pts, 3)
sc.doc.Objects.AddCurve(crv)
__result__ = {"point_count": len(pts), "length": crv.GetLength()}

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Loading the Rhino Plugin

1. Open Rhino 8
2. Open Script Editor: Tools > Python Script > Edit
3. Open startup.py (deployed by golem install-rhino) and click Run

GOLEM-3DMCP: Starting server on 127.0.0.1:9876...
GOLEM-3DMCP: Server started successfully!
GOLEM-3DMCP: 135 handler methods registered.

Auto-start on every Rhino launch: Tools > Options > RhinoScript > Startup Scripts > Add startup.py

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Configuration

Variable	Default	Description
GOLEM_RHINO_HOST	127.0.0.1	Rhino plugin host
GOLEM_RHINO_PORT	9876	Rhino plugin TCP port
GOLEM_GH_PORT	9877	Grasshopper sub-server port
GOLEM_TIMEOUT	30	Command timeout (seconds)
GOLEM_HEAVY_TIMEOUT	120	Heavy operation timeout (seconds)

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Requirements

Requirement	Version
Rhinoceros 3D	8.x (macOS)
Python	3.10+
macOS	12 Monterey or newer

The Rhino plugin runs inside Rhino's embedded Python 3.9 with zero external dependencies.

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Troubleshooting

Problem	Quick Fix
Connection refused	Start Rhino + run startup.py
Port already in use	lsof -i :9876 then kill the process
MCP server not in Claude	Check your MCP config JSON
Grasshopper tools fail	Open Grasshopper in Rhino first
Python version error	Need Python 3.10+ for MCP server

Run golem doctor to diagnose issues automatically.

See Troubleshooting Guide for detailed solutions.

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Documentation

• Architecture — System design, threading model, data flow
• Tool Reference — All 105 tools with parameters and examples
• Protocol Specification — TCP wire format, message framing, error codes
• Troubleshooting — Common issues and solutions

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Testing

# Unit tests (no Rhino needed)
pytest tests/ -v --ignore=tests/test_integration.py

# Full suite (integration tests auto-skip if Rhino not running)
pytest tests/ -v

# Integration tests only (requires Rhino + plugin running)
pytest tests/test_integration.py -v -m integration

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Branch Strategy

This repository uses two branches:

Branch	Purpose
main	GOLEM-3DMCP source development — features, bug fixes, docs
claude/pypi-package-setup-PMCI5	PyPI packaging & releases — build config, versioning, publish scripts

• Develop on main — all tool modules, Rhino plugin, tests, and documentation live here.
• Release from the PyPI branch — packaging structure (pyproject.toml, src/ layout, publish scripts) is managed separately so releases don't pollute the development history.

main                          ← development
  └── claude/pypi-package-setup-PMCI5  ← PyPI releases (pip install golem-3dmcp)

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Project Structure

golem-3dmcp/
├── src/golem_3dmcp/           # MCP Server (pip install golem-3dmcp)
│   ├── cli.py                 #   CLI entry point (golem command)
│   ├── server.py              #   FastMCP server
│   ├── connection.py          #   TCP client (singleton, thread-safe)
│   ├── protocol.py            #   Wire format: 4-byte length prefix + JSON
│   ├── config.py              #   Environment variable configuration
│   ├── models/                #   Pydantic data models
│   ├── tools/                 #   9 MCP tool modules
│   └── _rhino_plugin/         #   Bundled Rhino plugin (deployed via CLI)
├── tests/                     # 226 tests (pytest)
├── docs/                      # Architecture, protocol spec, tool reference
└── pyproject.toml             # Package definition

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Contributing

We welcome contributions! Here's how to get started:

Development Setup

# Clone the repository
git clone https://github.com/TheKingHippopotamus/GOLEM-3DMCP-Rhino-.git
cd GOLEM-3DMCP-Rhino-

# Create virtual environment (Python 3.10+ required)
python -m venv .venv
source .venv/bin/activate  # or .venv\Scripts\activate on Windows
pip install -e ".[dev]"

# Install pre-commit hooks
pre-commit install

Code Quality

All CI checks must pass before merging:

# Lint
ruff check src/ tests/

# Type check (strict mode)
mypy src/golem_3dmcp/ --ignore-missing-imports

# Unit tests (no Rhino needed)
pytest tests/ -v --ignore=tests/test_integration.py

# Integration tests (requires Rhino 8 + plugin running)
pytest tests/test_integration.py -v -m integration

Key Things to Know

• Two Python runtimes — The MCP server runs on Python 3.10+, but _rhino_plugin/ runs inside Rhino's embedded Python 3.9. They communicate over TCP. Don't add 3.10+ syntax to the plugin.
• _rhino_plugin/ is excluded from mypy — It uses Rhino-specific imports (Rhino.*, Grasshopper.*, clr) that don't exist in a standard environment.
• Tool registration — Tools use @mcp.tool() decorators. Each tool module imports mcp from server.py. Add new tools in src/golem_3dmcp/tools/ and register the module in server.py:main().
• Thread safety — RhinoConnection is a thread-safe singleton with a lock around socket I/O. Don't bypass send_command().
• Protocol — TCP messages use 4-byte length-prefixed JSON. See protocol.py for the wire format.

Pull Request Process

1. Create a feature branch from main
2. Make your changes
3. Ensure all checks pass (ruff, mypy, pytest)
4. Submit a PR with a clear description

See CONTRIBUTING.md for the full guide.

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License

MIT License. See LICENSE for details.

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MCP Server on Glama

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Credits

Created by King Hippopotamus
Built by NEXUS AI — 195 autonomous agents | 20 departments | 11 tiers

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Built with: FastMCP · RhinoCommon · rhinoscriptsyntax · Grasshopper SDK

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"From formless clay, through the power of words, form emerges."