Workshop 1: Agentic AI Design Orchestration using MCP

AAG2025: Advances in Architectural Geometry - Massachusetts Institute of Technology | 16—17 November 2025 | Workshop Page

Rhino Grasshopper MCP Server

A Model Context Protocol (MCP) server providing 30+ tools for interacting with Rhino 3D and Grasshopper through natural language. Features include parametric geometry generation, cross-file workflows, intelligent geometry transfer, and automated workflow suggestions. Uses an HTTP bridge architecture to handle Python version compatibility between MCP (Python 3.10+) and Rhino’s IronPython.

Architecture

┌─────────────────┐         ┌──────────────────┐         ┌─────────────┐
│   MCP Client    │ ◄─────► │   MCP Server     │ ◄─────► │   Rhino     │
│                 │   MCP   │ (Python 3.10+)   │  HTTP   │   Bridge    │
└─────────────────┘         └──────────────────┘         └─────────────┘
                                                              ▲
                                                              │
                                                         Rhino API
                                                         Grasshopper API

Key Features

• 30+ Tools - Comprehensive toolset for Rhino 3D and Grasshopper automation
• Smart Geometry Transfer - Automatically converts and validates geometry between files (Lines, Curves, Surfaces, Meshes, Breps)
• EML Convention - Automated parameter discovery using eml_ prefix for cross-file workflows
• Workflow Suggestions - JSON metadata system suggests file sequences and parameter connections
• File Management - Auto-launching Grasshopper, batch file operations, file verification
• DEBUG_MODE - Toggle verbose output via .env file for 60-80% token savings in production
• Custom Scripts - Execute Python code in Grasshopper with full access to component data
• Geometry Baking - User-controlled baking to Rhino with layer management and confirmation
• Auto-Discovery - Decorator-based tool registration - no manual configuration needed

Project Structure

MCP/

MCP server and client integration:

• main.py - MCP server with auto-discovery
• bridge_client.py - HTTP client for Rhino communication
• config/ - Configuration templates
• requirements.txt - Python 3.10+ dependencies

Rhino/

HTTP bridge server running inside Rhino:

• rhino_bridge_server.py - HTTP server (IronPython 2.7/3.9)
• start_rhino_bridge.py - Startup script

Tools/

Tool definitions with decorator-based auto-discovery:

• rhino_tools.py - Rhino 3D tools
• gh_tools.py - Grasshopper tools
• tool_registry.py - Auto-discovery system
• Grasshopper File Library/ - .gh file storage

Quick Start

1. Install MCP Server Dependencies

cd MCP/
pip install -r requirements.txt

2. Start Rhino Bridge Server

1. Open Rhino 8
2. Open Python Script Editor: Tools > Script > Edit
3. Load and run:

   exec(open(r'C:\path\to\rhino_gh_mcp\Rhino\start_rhino_bridge.py').read())
   

4. Verify: Visit http://localhost:8080/status

3. Configure MCP Client

Add to your MCP client configuration file (optional: if running in a virtual environment, you can point you command to that python executable):

{
  "mcpServers": {
    "rhino_gh": {
      "command": "python",
      "args": ["C:\\path\\to\\rhino_gh_mcp\\MCP\\main.py"]
    }
  }
}

4. Restart MCP Client

Restart your MCP client to load the server.

Configuration

DEBUG_MODE (Optional)

Control tool response verbosity to optimize token usage:

1. Copy .env.example to .env in project root
2. Set DEBUG_MODE=true for development or DEBUG_MODE=false for production
3. Restart Rhino bridge server to apply changes

Benefits:

• DEBUG_MODE=false - Saves 60-80% tokens by removing verbose debug logs (recommended for production)
• DEBUG_MODE=true - Full diagnostic output for troubleshooting

See Tools/README.md for detailed examples.

Workflow Metadata (Optional)

Add JSON metadata to describe Grasshopper files and enable workflow suggestions:

1. Create metadata.json in Tools/Grasshopper File Library/
2. Define file inputs, outputs, dependencies, and workflows
3. Use suggest_grasshopper_workflow tool for intelligent file sequence suggestions

Example metadata structure available in Tools/Grasshopper File Library/metadata.json.

Available Tools

Rhino Tools (5)

• draw_line_rhino - Draw lines in 3D space
• get_rhino_info - Get session information
• typical_roof_truss_generator - Generate parametric trusses
• get_selected_rhino_objects - Get selected object data
• get_rhino_object_geometry - Extract geometry

Grasshopper File Management (5)

• list_gh_files - List available .gh files
• open_gh_file - Open file (auto-launches Grasshopper)
• open_all_gh_files - Open all files at once
• get_active_gh_files - Get currently open files
• close_gh_file - Close specific file

EML Parameter Tools (4)

Convention-based tools using eml_ prefix for automated workflows:

• list_eml_parameters - Discover eml_ prefixed components
• get_eml_parameter_value - Extract parameter values
• set_eml_parameter_value - Set parameter values
• suggest_eml_connections - Suggest data flow connections

Cross-File Workflow Tools (2)

• transfer_eml_geometry_between_files - Direct geometry transfer
• execute_eml_workflow - Multi-file workflow orchestration

Traditional Grasshopper Tools (16)

• list_grasshopper_sliders / set_grasshopper_slider
• set_multiple_grasshopper_sliders
• analyze_grasshopper_sliders
• analyze_grasshopper_inputs_with_context
• analyze_grasshopper_outputs_with_context
• get_grasshopper_overview
• get_grasshopper_components
• list_grasshopper_valuelist_components
• set_grasshopper_valuelist_selection
• list_grasshopper_panels / set_grasshopper_panel_text
• get_grasshopper_panel_data
• set_grasshopper_geometry_input
• extract_grasshopper_geometry_output
• debug_grasshopper_state

Advanced Tools (5)

• bake_grasshopper_geometry - Bake geometry to Rhino with layer control
• execute_custom_grasshopper_script - Run Python in GH context
• suggest_grasshopper_workflow - Get workflow suggestions from metadata
• set_active_gh_file - Switch active document
• predict_truss_tonnage - Predict long span truss tonnage based on polynomial regression model from sample data

Using Grasshopper Files

IMPORTANT: Before using Grasshopper files with the MCP tools, ensure they are properly configured:

Prerequisites for Grasshopper Files:

1. Test files manually first - Open each .gh file directly in Grasshopper to verify it loads without errors
2. Install required plugins - Ensure all plugin dependencies are installed in Rhino/Grasshopper
3. Check file references - Verify any external file references or linked resources are accessible
4. Save files properly - Ensure files are saved in a stable state without errors

Common Issues:

• Files fail to open via MCP - Usually indicates missing plugins or file errors. Open manually in Grasshopper to see specific error messages.
• Timeout errors - File may be too large or have circular references causing slow solutions. Simplify or disable heavy components.

Only after verifying files work correctly in Grasshopper should you use them with MCP tools for automation.

Store verified .gh files in Tools/Grasshopper File Library/ for use with file management tools.

EML Convention

The eml_ (External ML) prefix enables automated component discovery in Grasshopper:

Supported Components:

Workflow Example:

1. Open generator.gh with eml_output_curve
2. Extract geometry using list_eml_parameters
3. Open processor.gh with eml_input_curve
4. Transfer using transfer_eml_geometry_between_files

This enables cross-file automation without manual rewiring.

Adding New Tools

Tools use decorator-based auto-discovery. Add both decorators to the same file:

# MCP tool (client-side)
@rhino_tool(name="create_circle", description="Create a circle...")
async def create_circle(center_x: float, center_y: float, radius: float):
    return call_bridge_api("/create_circle", {
        "center_x": center_x,
        "center_y": center_y,
        "radius": radius
    })

# Bridge handler (server-side)
@bridge_handler("/create_circle")
def handle_create_circle(data):
    import rhinoscriptsyntax as rs
    center = [data['center_x'], data['center_y'], 0]
    radius = data['radius']
    circle_id = rs.AddCircle(center, radius)
    return {"success": True, "circle_id": str(circle_id)}

Restart both servers to activate new tools.

Troubleshooting

Bridge server not responding:

• Check Rhino is open and bridge script is running
• Visit http://localhost:8080/status to verify
• Check port 8080 isn’t blocked by firewall

Tools not appearing:

• Verify MCP client config path is correct
• Restart MCP client after config changes
• Check MCP/main.py path uses absolute path

Grasshopper tools failing:

• Ensure Grasshopper plugin is loaded in Rhino
• Restart bridge server after code changes
• Check Rhino Python console for errors

Type errors in bridge:

• IronPython doesn’t support all type hints
• Use simple types or omit type hints in bridge handlers

Testing

1. Bridge Status: curl http://localhost:8080/status
2. List Endpoints: curl http://localhost:8080/info
3. Test Tool: Use MCP client to execute tools
4. Debug: Check Rhino Python console for bridge errors

Requirements

• Rhino 8 with Python support
• Python 3.10+ for MCP server
• Grasshopper (optional, for parametric tools)
• MCP-compatible client

License

MIT License

Author

Hossein Zargar (Seyed Hossein Zargar)