Develop and Debug ChatGPT Apps Locally with MCPJam

MCPJam offers a comprehensive suite of tools designed to streamline the local development, testing, and debugging of ChatGPT applications. Our platform eliminates common hurdles, providing a robust environment for building sophisticated AI experiences.

MCPJam Inspector: Local Development Client

The MCPJam Inspector serves as the dedicated local development client for the ChatGPT Apps SDK. It enables developers to build and thoroughly test their applications using a full widget emulator, removing the need for ngrok or an active ChatGPT subscription.

Get started instantly:

npx @mcpjam/inspector@latest

Alternatively, download our convenient desktop application for macOS or Windows.

ChatGPT Apps Builder: Advanced Debugging

Functioning like Chrome DevTools specifically for ChatGPT Apps, our Apps Builder provides an advanced emulator that exposes all windows.openai API calls and JSON-RPC traffic. This comprehensive tool fully simulates ChatGPT's behavior, offering unparalleled insight into your application's operations.

OAuth Debugger: Authorization Flow Validation

Visualize and debug your MCP authorization flows with precision. The OAuth debugger helps you verify that your OAuth implementation strictly conforms to the MCP specification at every step, ensuring secure and compliant user authentication.

LLM Playground: Model Emulation & Testing

Experience 1:1 emulation with ChatGPT in our LLM Playground. Test your ChatGPT App against a variety of models, including frontier models like GPT-5, which are provided for free. The playground offers different display modes for versatile testing and analysis.

Connect With Us

We are eager to assist with your MCP strategy and development needs. Share details about your project, and our team will get in touch to discuss how MCPJam can support your vision. You can also reach us directly via email at founders@mcpjam.com.