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Skybridge provides two ways to test your app: local DevTools for rapid iteration, and ChatGPT for integration testing. Open http://localhost:3000/ in your browser to access DevTools. This is the fastest way to develop:
  • Tool listing - See all registered tools and widgets
  • Input forms - Test tools with custom inputs
  • Widget preview - Render widgets in a mocked ChatGPT environment
  • Theme/locale switching - Test different display modes
The DevTools mock the window.openai API, so your widget code works identically in both environments.
Fast IterationFor full details on the emulator, HMR, and Vite plugin, see Fast Iteration.
Want LLM-based conversations locally?For complete local emulation with real LLM conversations, check out MCP Jam - a third-party tool that provides a full ChatGPT-like environment for testing MCP servers.

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Testing in ChatGPT

When you’re ready to test the full integration with the LLM:

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1. Expose your server

ChatGPT needs a public URL. Use ngrok to expose your local server: 
ngrok http 3000
Copy the forwarding URL (e.g., https://abc123.ngrok-free.app).

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2. Connect to ChatGPT

  1. In ChatGPT, go to Profile → Apps → Create app
  2. Enter your ngrok URL with /mcp at the end: 
    https://abc123.ngrok-free.app/mcp
  3. Click Create

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3. Test your app

  1. Start a new conversation
  2. Select your app using the + button
  3. Prompt the model to trigger your tools

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Hot Module Reload

Widget changes in web/src/widgets/ appear instantly in ChatGPT without reconnecting. Server changes in server/src/ require starting a new conversation to take effect.

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What’s Next?

Core Concepts

Learn how Skybridge extends the raw APIs with React hooks

Guides

Learn patterns for data fetching, state management, and more