Unofficial Jules MCP Server

jules-mcp-server connects your AI coding assistant (such as Claude, Cursor, or Copilot) to the Jules API, enabling autonomous coding sessions directly from your IDE. It acts as a Model Context Protocol (MCP) server, giving your AI assistant the ability to create coding sessions, manage tasks, and interact with Jules agents for automated software development.

Changelog | Troubleshooting

Key features

• Autonomous coding sessions: Create and manage Jules coding sessions directly from your AI assistant

• GitHub integration: Connect to your GitHub repositories through Jules sources

• Plan approval workflow: Review and approve execution plans before Jules makes changes

• Real-time activity tracking: Monitor session progress and view detailed activity logs

• Type-safe validation: Runtime validation with Zod ensures all inputs are validated before API calls

• Streamable HTTP transport: Uses the MCP Streamable HTTP specification for reliable communication

Disclaimers

jules-mcp-server provides your MCP client with access to create and manage coding sessions in your connected GitHub repositories. Ensure you review and approve plans before execution, especially in production repositories. The server requires a valid Jules API key with appropriate permissions.

Requirements

• Node.js v18 or newer

• Jules API account with API key

• npm

Getting started

1. Clone and install

2. Configure environment

Your .env file should contain:

3. Start the server

For production:

4. Configure your MCP client

Add the following config to your MCP client:

MCP Client configuration

Edit your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

Add the Jules server configuration:

Restart Claude Desktop after saving the configuration.

Manual installation:

1. Go to Cursor Settings → Features → MCP

2. Click Add new global MCP server

3. Add the configuration:

4. Restart Cursor

Follow the MCP installation guide and use the configuration provided above.

For other MCP clients that support Streamable HTTP transport, use the configuration provided above. Ensure the client supports:

• MCP protocol version 2024-11-05 or newer

• Streamable HTTP transport (type: "streamable-http")

• Stateless mode (no session management required)

Your first prompt

Enter the following prompt in your MCP client to verify the setup:

Your MCP client should call the jules_list_sources tool and display your connected GitHub repositories.

To create a coding session:

Tools

All tools include runtime validation with Zod for type safety and clear error messages.

• Session management (3 tools)

  • jules_create_session - Create a new Jules coding session

  • jules_list_sessions - List all your Jules sessions

  • jules_send_message - Send a message to an active Jules agent

• Plan approval (1 tool)

  • jules_approve_plan - Approve a session's execution plan

• Monitoring (2 tools)

  • jules_list_sources - List your connected GitHub sources

  • jules_list_activities - List activities for a session

Tool details

jules_list_sources

List your connected GitHub sources.

Parameters:

• pageSize (optional): Number of items per page (1-100)

• pageToken (optional): Token for pagination

jules_create_session

Create a new Jules coding session.

Parameters:

• prompt (required): The task prompt for Jules (1-10000 characters)

• source (required): Source path, e.g., sources/github/owner/repo

• title (optional): Session title (1-200 characters)

• startingBranch (optional): Git branch to start from (default: main)

• requirePlanApproval (optional): Whether to require plan approval before execution (default: false)

jules_list_sessions

List all your Jules sessions.

Parameters:

• pageSize (optional): Number of items per page (1-100)

• pageToken (optional): Token for pagination

jules_approve_plan

Approve a session's execution plan.

Parameters:

• sessionId (required): The session ID to approve, format: sessions/{id}

jules_send_message

Send a message to an active Jules agent.

Parameters:

• sessionId (required): The session ID, format: sessions/{id}

• prompt (required): The message to send (1-10000 characters)

jules_list_activities

List activities for a session.

Parameters:

• sessionId (required): The session ID, format: sessions/{id}

• pageSize (optional): Number of items per page (1-100)

• pageToken (optional): Token for pagination

Resources

The server provides two MCP resources for additional context:

• jules://sources - Your connected GitHub sources

• jules://sessions/{id}/activities - Latest activities for a specific session

Resources can be accessed directly by MCP clients for context gathering.

Configuration

The Jules MCP server supports the following environment variables:

• JULES_API_KEY (required) Your Jules API key for authentication.

  • Type: string

• PORT Port number for the HTTP server.

  • Type: number

  • Default: 3323

• HOST Host address to bind the server to.

  • Type: string

  • Default: 127.0.0.1

• ALLOWED_ORIGINS Comma-separated list of allowed origins for CORS.

  • Type: string

  • Default: null,http://localhost

Configure these in your .env file:

Architecture

Stateless mode

The server runs in stateless mode (no session management) for optimal compatibility with MCP clients like Cursor. Each request is independent and doesn't require session ID headers.

Transport

Uses the MCP Streamable HTTP transport specification with:

• JSON responses enabled (enableJsonResponse: true)

• No session management (sessionIdGenerator: undefined)

• CORS protection with configurable origins

• Request/response logging for debugging

Validation

All tool inputs are validated using Zod schemas before making API calls:

• Prevents invalid requests from reaching the Jules API

• Provides clear, actionable error messages

• Saves API quota by catching errors early

• Ensures type safety throughout the request pipeline

See VALIDATION_EXAMPLES.md for detailed validation rules and examples.

Troubleshooting

Server won't start

Problem: Server fails to start or crashes immediately.

Solutions:

• Verify JULES_API_KEY is set in .env

• Check that port 3323 is not already in use: netstat -ano | findstr :3323 (Windows) or lsof -i :3323 (macOS/Linux)

• Ensure Node.js version is 18 or newer: node --version

• Check server logs for specific error messages

Cursor shows "No tools"

Problem: MCP connection appears to work, but no tools are listed.

Solutions:

• Verify the server is running: curl http://127.0.0.1:3323/mcp should not return connection errors

• Restart Cursor after making configuration changes

• Check that the URL in your config is exactly http://127.0.0.1:3323/mcp

• Ensure the server is using stateless mode (default configuration)

• Try restarting the server: stop it and run npm run dev again

CORS/Origin errors

Problem: Server returns 403 Forbidden Origin errors.

Solutions:

• Add null to ALLOWED_ORIGINS in .env for local development

• For custom origins, update ALLOWED_ORIGINS: ALLOWED_ORIGINS=null,http://localhost,http://127.0.0.1

• Restart the server after changing environment variables

Validation errors

Problem: Tool calls fail with validation errors.

Solutions:

• Check the error message for specific field requirements

• Verify session IDs match the format sessions/{id}

• Verify source paths match the format sources/github/owner/repo

• Ensure string lengths are within specified limits

• See VALIDATION_EXAMPLES.md for correct input formats

API authentication errors

Problem: Tools fail with 401 Unauthorized errors.

Solutions:

• Verify your JULES_API_KEY is valid and active

• Check that the API key has the necessary permissions

• Ensure the .env file is in the project root directory

• Restart the server after updating the API key

Connection timeouts

Problem: Requests to Jules API timeout or hang.

Solutions:

• Check your internet connection

• Verify Jules API status at status.jules.ai (if available)

• Increase timeout values if working with large repositories

• Check firewall settings that might block outgoing HTTPS requests

Development

Building from source

The TypeScript source in src/ compiles to JavaScript in dist/.

Running in development mode

This uses tsx to run TypeScript directly with hot reloading.

Project structure

Known limitations

Streamable HTTP client support

Not all MCP clients fully support the Streamable HTTP transport. This server is tested with:

• ✅ Cursor (stateless mode)

• ✅ Claude Desktop (with manual configuration)

• ⚠️ VS Code/Copilot (limited support, check version)

Session management

The server uses stateless mode for compatibility. If you need stateful session management, you can modify src/server.ts to enable sessionIdGenerator, but this may break compatibility with some clients like Cursor.

Local-only access

By default, the server binds to 127.0.0.1 (localhost only) for security. To allow remote access, change the HOST environment variable, but ensure you implement proper authentication and use HTTPS in production.

Contributing

Contributions are welcome! Please:

1. Fork the repository

2. Create a feature branch

3. Make your changes with tests

4. Submit a pull request

License

MIT License - see LICENSE file for details.

Support

• Issues: GitHub Issues

• Jules API: jules API

• MCP Specification: modelcontextprotocol.io