Test Your App

frac apps expose a normal HTTP MCP endpoint, so you can test locally with MCP tooling and then connect the same endpoint to compatible clients.

Local Development (Recommended)

Start your development server:

npm run dev

Your MCP server will be available at http://localhost:3000/mcp.

Production Testing

When you’re ready to test your AI App with an LLM, deploy the server or expose it through your own tunnel so the client can reach your /mcp endpoint.

Test with ChatGPT using the Apps SDK runtime

Test with Claude using the MCP Apps runtime

Test locally with VSCode, Goose, and other desktop clients

Testing in ChatGPT

ChatGPT uses the Apps SDK runtime and requires a public URL to connect to your app.

1. Expose your server

ChatGPT needs a public URL to access your AI App. Deploy your server or use your preferred tunnel provider, then keep the /mcp path on the URL.

2. Connect to ChatGPT

In ChatGPT, go to Profile → Apps → Create app
Enter your public /mcp URL:
```
https://your-domain.example/mcp
```
Click Create

3. Test your app

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

Hot Module Reload

View changes in src/views/ appear instantly without reconnecting.

Server changes in src/server.ts require starting a new conversation to take effect.

Testing in Claude

Claude uses the MCP Apps runtime and requires a public URL to connect to your app.

1. Expose your server

Claude needs a public URL to access your AI App. Deploy your server or use your preferred tunnel provider, then keep the /mcp path on the URL.

2. Connect to Claude

In Claude, go to Settings → Connectors → Add Custom Connector and configure your MCP server connection
Enter your App name and public /mcp URL:
```
https://your-domain.example/mcp
```
Click on Add

3. Test your app

Start a new conversation in Claude
Make sure your Connector is selected in the Connectors dropdown
Test view interactions and tool responses

Testing in other MCP Clients

Desktop MCP clients like VSCode, Goose, and others can connect directly to your local server without needing a HTTP tunnel or a public URL.

1. Start your server

Make sure your development server is running:

npm run dev

Your MCP server will be available at http://localhost:3000/mcp.

2. Connect to your MCP client

Connect your server to any desktop MCP client that supports the ext-apps specification, such as VSCode, Goose, Postman, or MCPJam.

3. Test your app

Configure your MCP client to connect to http://localhost:3000/mcp
Start a conversation in your MCP client
Test your app by invoking tools and interacting with the views

What’s Next?

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Learn patterns for data fetching, state management, and more