MCP Marionette

The MCP Marionette server provides a bridge for AI agents to interact with humans for decision-making, clarification, and session steering. It implements the Model Context Protocol (MCP) to allow agents to pause their execution and wait for human input through structured forms.

Purpose

This server enables human-in-the-loop workflows where an agent can:

• Ask clarifying questions with predefined options.
• Request confirmation before performing sensitive actions.
• Allow humans to steer or redirect the session goal.

Why Use This with GitHub Copilot?

Cost Savings: Premium Requests vs. Tokens

GitHub Copilot uses a premium request pricing model, not token-based billing. This has important implications for how you interact with Copilot:

Key insight: Every chat message, agent mode prompt, and complex interaction consumes premium requests. Once you hit your limit, you pay $0.04 per additional request.

How MCP Marionette Saves You Money

Using this MCP server with GitHub Copilot in VS Code provides significant cost benefits:

1. Structured Responses Reduce Back-and-Forth

Without MCP Marionette:

User: "Should I use React or Vue for this project?"
Copilot: "Great question! Both have pros and cons..."
[Multiple chat turns = Multiple premium requests]

With MCP Marionette:

User: "Ask me which framework to use with options React, Vue, Svelte"
Copilot: [Uses askQuestion tool → Single premium request]
Human: [Selects from dropdown: "React - Component-based, large ecosystem"]
Copilot: [Proceeds with React implementation]

Result: 1 premium request instead of 3-5 for clarifying questions.

2. Session Steering Prevents Wasted Requests

Without steering:

Copilot: [Works on wrong task for 10 turns]
User: "Wait, that's not what I wanted"
Copilot: "Sorry, let me restart..."
[All previous requests consumed premium quota]

With steerSession:

User: "Check if the agent is on track"
Copilot: [Uses steerSession → Human sees current goal]
Human: "Redirect to focus on API layer first"
Copilot: [Pivots immediately]

Result: Prevents wasted premium requests on incorrect directions.

3. Agent Mode Efficiency

GitHub Copilot's agent mode is powerful but premium-request intensive. Each autonomous action counts. By adding human checkpoints:

• Agent asks before risky operations
• Human confirms expensive refactors
• Direction changes happen early, not after wasted work

Example: Cost Comparison

Scenario: Implementing a new feature with architecture decisions

For a developer doing 50 complex tasks/month:

• Without MCP: 1,000 premium requests → Exceeds Pro limit, costs $28 extra
• With MCP: 350 premium requests → Well within Pro limit, $0 extra

GitHub Copilot + MCP Setup

GitHub Copilot in VS Code supports MCP servers natively. Here's how to use MCP Marionette:

Step 1: Configure MCP in VS Code

Create or edit .vscode/mcp.json in your project:

{
  "servers": {
    "marionette": {
      "command": "npx",
      "args": ["-y", "mcp-marionette"]
    }
  }
}

Or use the full path for local development:

{
  "servers": {
    "marionette": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/TO/mcp-marionette/dist/index.js"]
    }
  }
}

Step 2: Enable MCP in Copilot

1. Open VS Code Settings (Cmd+, / Ctrl+,)
2. Search for "copilot mcp"
3. Enable github.copilot.chat.mcp.enabled

Or add to your settings.json:

{
  "chat.mcp.discovery.enabled": true
}

Step 3: Use in Copilot Chat

1. Open Copilot Chat (click the chat icon)
2. Select Agent mode from the dropdown
3. Click the tools icon (🔧) to see available MCP tools
4. Your askQuestion and steerSession tools appear under "MCP"

Step 4: Use Tools in Conversations

You: "I need to implement user authentication. Ask me which auth method to use."

Copilot: [Calls askQuestion tool]
Human sees form: "Which authentication method?"
- OAuth 2.0 - Third-party login (Google, GitHub, etc.)
- Email/Password - Traditional login
- Magic Links - Passwordless email login

[Human selects: "OAuth 2.0 - Third-party login"]

Copilot: "I'll implement OAuth 2.0 authentication..."

When to Use MCP Marionette with Copilot

Key Takeaway

MCP tools don't consume extra premium requests - they're part of the agent's tool execution. The human response happens in the VS Code UI, not in the chat. This means:

• 1 chat message + 1 tool call = 1 premium request (not 2)
• Structured answers prevent follow-up questions
• Session steering catches wrong directions early

For Copilot users, this MCP server pays for itself by reducing premium request usage by 50-70% on complex tasks.

Installation

Prerequisites

• Node.js 18+ - Required to run the server
• npm - Comes with Node.js

Installation Methods

Method 1: Clone and Build (Recommended for Development)

git clone <repository-url>
cd mcp-marionette
npm install
npm run build

Method 2: Global npm Installation

npm install -g mcp-marionette
mcp-marionette  # Run directly

Method 3: Using npx (No Installation Required)

npx -y mcp-marionette

Configuration

The MCP Marionette server must be configured in your MCP client's configuration file. Below are instructions for different MCP clients.

Configuration File Locations

Claude Desktop Configuration

Step 1: Find the Configuration File

macOS:

~/Library/Application Support/Claude/claude_desktop_config.json

Windows:

%APPDATA%\Claude\claude_desktop_config.json

Linux:

~/.config/Claude/claude_desktop_config.json

Step 2: Edit the Configuration

Add the following to your claude_desktop_config.json:

Option A: Direct path (if cloned locally):

{
  "mcpServers": {
    "marionette": {
      "command": "node",
      "args": [
        "/ABSOLUTE/PATH/TO/mcp-marionette/dist/index.js"
      ]
    }
  }
}

Option B: Using npx (no local clone needed):

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

Option C: Global installation:

{
  "mcpServers": {
    "marionette": {
      "command": "mcp-marionette"
    }
  }
}

Important Notes:

• Use absolute paths (not relative paths)
• On Windows, use forward slashes / or double backslashes \\
• Claude Desktop only reads this file at startup

Step 3: Restart Claude Desktop

After saving the configuration file, completely restart Claude Desktop for changes to take effect.

Step 4: Verify Installation

Look for the 🔨 (hammer) icon in Claude Desktop's chat interface. This indicates MCP tools are loaded.

Claude Code Configuration

Option 1: Using CLI Commands

Add the server using Claude Code's CLI:

# For local development
claude mcp add --transport stdio marionette -- node /absolute/path/to/mcp-marionette/dist/index.js

# For global installation
claude mcp add --transport stdio marionette -- mcp-marionette

# For npx
claude mcp add --transport stdio marionette -- npx -y mcp-marionette

Option 2: JSON Configuration

Create or edit .claude/settings.json in your project root:

{
  "mcpServers": {
    "marionette": {
      "command": "node",
      "args": [
        "/ABSOLUTE/PATH/TO/mcp-marionette/dist/index.js"
      ]
    }
  }
}

Or for global configuration, edit ~/.claude.json.

Claude Code supports hot-reloading of MCP servers, so you don't need to restart.

Verify in Claude Code

Run /mcp in Claude Code to see loaded MCP servers.

Cursor Configuration

Cursor uses the same mcpServers format as Claude Desktop.

Global (all projects):

~/.cursor/mcp.json

Project-scoped:

.cursor/mcp.json

Example:

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

Cline (VS Code) Configuration

File location:

~/.vscode/User/globalStorage/saoudrizwan.claude-dev/settings/cline_mcp_settings.json

Example:

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

How Agents Discover This Server

Once configured, your MCP client will automatically discover and connect to the server:

Discovery Flow

1. Server Spawn: MCP client spawns the server process using the configured command and args
2. Initialize: Client and server perform capability negotiation via JSON-RPC
3. Tool Discovery: Client calls tools/list to discover available tools
4. Tool Registration: Client registers askQuestion and steerSession with the agent

Architecture Diagram

┌─────────────┐     ┌──────────────┐     ┌─────────────────────┐
│   Agent     │◄───►│  MCP Client  │◄───►│  MCP Marionette   │
│  (Claude)   │     │ (Desktop/    │     │      Server         │
│             │     │   Code/etc)  │     │                     │
└─────────────┘     └──────────────┘     └─────────────────────┘
                            │
                            │ 1. Spawn process
                            │ 2. Initialize connection
                            │ 3. Discover tools
                            │ 4. Register tools
                            ▼
                     [askQuestion, steerSession]

The agent automatically discovers these tools and can invoke them during conversations.

Tool Documentation

askQuestion

Asks a structured question with predefined options and an optional custom response field.

Input Parameters

Output Format

Returns the selected answer or custom response as text and structured data.

Success Response:

{
  "content": [{ "type": "text", "text": "Staging" }],
  "structuredContent": {
    "sessionId": "deploy-task-456",
    "action": "accept",
    "answer": "Staging"
  }
}

Custom Response:

{
  "content": [{ "type": "text", "text": "Deploy to canary first" }],
  "structuredContent": {
    "sessionId": "deploy-task-456",
    "action": "accept",
    "answer": "Deploy to canary first"
  }
}

Example Usage

{
  "sessionId": "deploy-task-456",
  "header": "Deployment Target",
  "question": "Which environment should we deploy the latest changes to?",
  "options": [
    { "label": "Staging", "description": "Internal testing environment" },
    { "label": "Production", "description": "Live environment for all users" }
  ],
  "multiple": false
}

steerSession

Allows humans to provide high-level direction to an active agent session.

Input Parameters

Output Format

Returns a structured object containing:

• directive: One of continue, pause, modify, redirect, terminate, or custom.
• newGoal: The updated goal if the directive is modify or redirect.
• customInstructions: Additional details provided by the human.
• sessionStatus: The resulting status of the session (e.g., active, paused, terminated).

Example Response:

{
  "content": [{ 
    "type": "text", 
    "text": "{\"directive\":\"modify\",\"newGoal\":\"Focus on MCP server architecture\",\"customInstructions\":\"Include diagrams\",\"sessionStatus\":\"active\"}" 
  }],
  "structuredContent": {
    "sessionId": "research-session-789",
    "directive": "modify",
    "newGoal": "Focus on MCP server architecture",
    "customInstructions": "Include diagrams",
    "sessionStatus": "active"
  }
}

Example Usage

{
  "sessionId": "research-session-789",
  "currentGoal": "Find all competitors in the MCP ecosystem"
}

Quick Start Examples

Example 1: Ask a Simple Question

Agent Request:

{
  "sessionId": "planning-session-001",
  "header": "Approach",
  "question": "Which approach should we take?",
  "options": [
    { "label": "Quick", "description": "Fast but basic implementation" },
    { "label": "Thorough", "description": "Comprehensive with tests" }
  ]
}

Human Sees:

• Header: "Approach"
• Question: "Which approach should we take?"
• Options: "Quick - Fast but basic implementation" and "Thorough - Comprehensive with tests"
• Custom text input field

Example 2: Steering a Session

Agent Request:

{
  "sessionId": "coding-task-123",
  "currentGoal": "Refactor the authentication module"
}

Human Sees:

• Session steering form
• Current goal: "Refactor the authentication module"
• Directive options: continue, pause, modify, redirect, terminate, custom
• Fields for new goal and custom instructions

Troubleshooting

Common Issues

Server Not Appearing

Symptoms: The 🔨 icon doesn't show in Claude Desktop.

Solutions:

1. Check file paths - Use absolute paths, not relative
2. Verify build - Run npm run build and ensure dist/index.js exists
3. Restart client - Claude Desktop requires a full restart
4. Check JSON syntax - Validate your config at https://jsonlint.com/

Permission Denied

Symptoms: EACCES: permission denied

Solution:

# Make the server executable
chmod +x dist/index.js

PATH Issues

Symptoms: command not found or spawn ENOENT

Solutions:

1. Use the full path to node:

   {
     "command": "/usr/local/bin/node",
     "args": ["/path/to/mcp-marionette/dist/index.js"]
   }
   

2. Find node path:

   which node  # macOS/Linux
   where node  # Windows
   

npx Issues

Symptoms: npx: command not found or slow startups

Solutions:

1. Clear npx cache:

   rm -rf ~/.npm/_npx
   

2. Use global installation instead:

   npm install -g mcp-marionette
   

3. Use direct node path instead of npx

"import: command not found"

Symptoms: Server fails with /bin/sh: import: command not found

Cause: Missing shebang in compiled file

Solution: Rebuild with shebang:

npm run build
# Then manually add to top of dist/index.js:
#!/usr/bin/env node

Debugging Steps

1. Test the server directly:

   node dist/index.js
   

   If the server starts without errors, it's working correctly.

2. Check MCP logs:

   • Claude Desktop (macOS): ~/Library/Logs/Claude/mcp.log
   • Cursor: Output panel → MCP server dropdown

3. Verify JSON-RPC communication:

   echo '{"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{},"clientInfo":{"name":"test","version":"1.0.0"}},"id":1}' | node dist/index.js
   

4. Check for stdout writes: Ensure your server doesn't write to stdout (only stderr). Writing to stdout corrupts JSON-RPC messages.

Client Comparison

Development

Project Structure

mcp-marionette/
├── package.json          # Dependencies and scripts
├── tsconfig.json         # TypeScript configuration
├── README.md            # This file
├── src/
│   └── index.ts         # Server implementation
└── dist/                # Compiled output
    ├── index.js
    ├── index.d.ts
    └── index.js.map

Building

npm run build

Testing

# Test the server directly
node dist/index.js

# Or test with npx
npx -y mcp-marionette

Publishing

# Build before publishing
npm run build

# Publish to npm
npm publish

# Or publish as beta
npm publish --tag beta

Security Considerations

• Local Execution: This server runs locally on your machine
• No External Network: No external network connections are made
• User Approval: All tool executions require explicit user approval in MCP clients
• Data Privacy: No data is sent to external services
• Session Isolation: Each session is identified but not persisted

Environment Variables

The server supports the following environment variables:

Configure in your MCP client config:

{
  "mcpServers": {
    "marionette": {
      "command": "node",
      "args": ["/path/to/dist/index.js"],
      "env": {
        "NODE_ENV": "development"
      }
    }
  }
}

License

MIT

Contributing

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

Support

For issues and questions:

• GitHub Issues: github.com/yourusername/mcp-marionette/issues
• MCP Documentation: modelcontextprotocol.io