MCP Apps Generative UI Showcase

https://github.com/user-attachments/assets/48eeab8d-7845-4d06-83ef-d518a807da03

Book flights, reserve hotels, manage portfolios, and run a kanban board - all inside the chat. Built with CopilotKit, AG-UI, and MCP Apps, showcasing the MCP Apps Extension (SEP-1865) for rendering interactive UIs directly in the chat.

Gen UI concept - sandboxed in-chat apps over a tool protocol. The MCP server registers tools (workout-generator, create-portfolio, create-board…) and links each to an HTML/JS resource via _meta["ui/resourceUri"]. When the agent calls a tool, CopilotKit mounts the linked app as a sandboxed iframe in the chat; the iframe talks back to MCP tools over JSON-RPC postMessage. Result: full, interactive product surfaces (multi-step wizards, drag-drop boards, live charts) running inline - server-owned logic, chat-owned presentation.

Live Demo

https://web-app-production-9af6.up.railway.app

Featured Apps

Quick Start

1. Install Dependencies

# From the mcp-apps directory
npm install

cd mcp-server
npm install
cd ..

2. Set Environment Variables

Create .env.local in the mcp-apps directory:

OPENAI_API_KEY=sk-...

3. Build & Run

# Terminal 1: Build and run MCP Server
cd mcp-server
npm run build
npm run dev
# Server runs at http://localhost:3001/mcp

# Terminal 2: Run Next.js Frontend (from mcp-apps directory)
npm run dev
# Frontend at http://localhost:3000

Open http://localhost:3000 and try one of the example prompts!

How It Works

MCP Apps are interactive HTML/JS applications that render in sandboxed iframes within the chat sidebar. They communicate with the MCP server via JSON-RPC over postMessage.

User: "Book a flight from JFK to LAX"
        ↓
AI calls search-flights tool
        ↓
MCPAppsMiddleware intercepts, fetches HTML resource
        ↓
CopilotKit renders flights-app.html in iframe
        ↓
User interacts with wizard UI
        ↓
UI calls MCP tools via postMessage → server

Tool Registration Pattern

// Tool declares its UI resource via _meta
server.registerTool(
  "search-flights",
  {
    inputSchema: { origin, destination, departureDate, passengers },
    _meta: { "ui/resourceUri": "ui://flights/flights-app.html" },
  },
  handler,
);

// Resource serves the HTML
server.registerResource(
  "flights-app",
  "ui://flights/flights-app.html",
  {
    mimeType: "text/html+mcp", // Marks as MCP App
  },
  () => ({ contents: [{ text: htmlContent }] }),
);

Project Structure

mcp-apps/
├── src/app/
│   ├── page.tsx                    # Main demo page
│   └── api/copilotkit/route.ts     # CopilotKit + MCPAppsMiddleware
├── mcp-server/
│   ├── server.ts                   # MCP server with all tools
│   ├── src/
│   │   ├── flights.ts              # 15 airports, 6 airlines
│   │   ├── hotels.ts               # 10 cities, 30 hotels
│   │   ├── stocks.ts               # 18 stocks, portfolios
│   │   └── kanban.ts               # Board templates
│   └── apps/
│       ├── flights-app.html        # Airline booking wizard
│       ├── hotels-app.html         # Hotel booking wizard
│       ├── trading-app.html        # Investment simulator
│       └── kanban-app.html         # Kanban board
└── README.md

Key Technologies

• CopilotKit (@copilotkit/*) - AI chat interface with MCP Apps support
• AG-UI MCP Apps Middleware - Bridges MCP servers with CopilotKit
• MCP SDK (@modelcontextprotocol/sdk) - Model Context Protocol server
• Vite - Bundles each app into single self-contained HTML files

Deployment

The demo is deployed on Railway with two services:

For production, set MCP_SERVER_URL environment variable to point to your deployed MCP server.