How to Build a ChatGPT App

Abe Wheeler November 28, 2025

ChatGPT Apps MCP Apps Getting Started Tutorial

A simple counter app built and deployed with sunpeak.

[Updated 2026-02-05] There isn’t much content out there to help developers build their ChatGPT Apps, so I figured I’d do a quick consolidation & write-up.

TL;DR: Official resources include the OpenAI ChatGPT Apps docs, example apps, and apps-sdk-ui library. Use sunpeak to quickstart with a local simulator and ngrok for ChatGPT connection.

As far as I’ve seen, this is the extent of the official Apps SDK tooling, which has been supplanted by MCP App support:

OpenAI ChatGPT Apps Documentation (launched 10/6) - overall documentation.
openai/openai-apps-sdk-examples (launched 10/6) - 7 example apps.
openai/apps-sdk-ui (launched 11/21) - low-level React component library consistent with the design requirements.
MCP App Extension protocol (launched 11/21) - generic protocol of the ChatGPT App runtime/interface.

These resources provide the foundation for getting started with ChatGPT App development. The documentation covers the basics, the example apps show you patterns to follow, and the UI library gives you the building blocks for creating interfaces that feel native to ChatGPT.

Getting Started

The quickest way to get started building ChatGPT Apps is with sunpeak, a ChatGPT App Framework built on the MCP Apps protocol that provides everything you need to create, develop, and deploy your first ChatGPT App.

1. Install sunpeak & Create a Project

First, make sure you have Node.js 20+ installed. Then install sunpeak globally and create a new project:

pnpm add -g sunpeak && sunpeak new
cd my-app

2. Local Development Server

Run the development environment to access a built-in ChatGPT simulator:

pnpm dev

Access the simulator at http://localhost:6767. The interface updates automatically as you modify components.

In another terminal, create a tunnel so ChatGPT can connect:

ngrok http 6766

Configure the tunnel URL with /mcp path in ChatGPT settings under “User > Settings > Apps & Connectors > Create”

Your app is now running in ChatGPT!

For more details, check out the sunpeak documentation.

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Frequently Asked Questions

What is the fastest way to build a ChatGPT App?

Use sunpeak, the ChatGPT App framework (built on MCP). Run "pnpm add -g sunpeak && sunpeak new" to create a project with all dependencies configured, then "sunpeak dev" to start a local development server with a built-in ChatGPT simulator at localhost:6767.

Do I need a paid ChatGPT subscription to develop ChatGPT Apps?

No. You can develop and test ChatGPT Apps locally using sunpeak's built-in ChatGPT simulator without any ChatGPT account. A paid ChatGPT Plus or Team subscription with developer mode is only needed when connecting your ChatGPT App (MCP App) to the real ChatGPT.

How do I connect my ChatGPT App to the real ChatGPT?

Run your MCP server with "sunpeak dev", create a tunnel using ngrok (ngrok http 6766), then add the ngrok URL with /mcp path in ChatGPT under User > Settings > Apps & Connectors > Create. Requires a paid account with developer mode.

What is sunpeak and why should I use it for ChatGPT App development?

Sunpeak is an open-source ChatGPT App framework (built as an MCP App framework) described as "Next.js for ChatGPT Apps." It provides a ChatGPT simulator, pre-built UI components based on apps-sdk-ui, an MCP server with hot reloading, and CLI tools for building and deploying apps.

What Node.js version do I need for ChatGPT App development?

You need Node.js version 20 or higher to use sunpeak and build ChatGPT Apps. Check your version with "node --version" and update if needed before running sunpeak commands.

What is the apps-sdk-ui component library for ChatGPT Apps?

apps-sdk-ui is OpenAI's official React component library for building ChatGPT Apps (MCP Apps) that follow ChatGPT's design guidelines. Sunpeak includes production-ready components built on top of apps-sdk-ui for faster ChatGPT App development.

What is the MCP App Extension protocol for ChatGPT Apps?

The MCP App Extension protocol defines how ChatGPT Apps interact with ChatGPT through the Model Context Protocol. It specifies how Resources (UI views) and Tools (API actions) are structured and communicated between your ChatGPT App and ChatGPT. Sunpeak handles this protocol for you automatically.