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Test an existing MCP server

Add automated testing to any MCP server (Python, Go, TypeScript, Rust, or any language). No project changes required.

Build a new MCP App

Create a new MCP App project with interactive UIs, tools, and testing built in. Follow the steps below.

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New projects

1

Create a project

Requirements: Node.js 20+
npx sunpeak new sunpeak-app
cd sunpeak-app
2

Develop locally

Start the development server:
pnpm dev
This starts:
  • The MCP App inspector at http://localhost:3000 for local development
  • An MCP server at http://localhost:8000 for testing with real hosts like ChatGPT
Both servers support Hot Module Reload - your changes reflect instantly!
3

Test in a host (ChatGPT)

Run a tunnel to allow ChatGPT to connect to your local MCP server:
# In another terminal, run a tunnel. For example:
ngrok http 8000
Adding a custom app requires Developer mode. If it is not already enabled, click your user menu in the bottom-left corner and select Settings > Security and login > Developer mode.Then return to the ChatGPT homepage and click Plugins in the sidebar. Open your app if it is already there, or select the + button and add the tunnel Forwarding URL at the /mcp path (for example, https://your-random-subdomain.ngrok-free.dev/mcp).ChatGPT creates a developer-mode app backed by your MCP server. It appears under Plugins, but its MCP App UI and runtime do not change.
4

Build & start for production

Build your resources and tools, then start the production MCP server:
pnpm build && pnpm start
This compiles your tool handlers, Zod schemas, and optional auth from src/server.ts, then starts a production MCP server on port 8000.

Project Scaffold

Explore your new MCP App project.

Deployment Guide

Deploy your app to production.