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b6fc151094Provides context about this repository including: - Common commands for building, testing, and running examples - SDK entry points and their purposes - Communication flow between Guest UI, Host, and MCP Server - Key source files and their responsibilities - Protocol lifecycle from initialization to teardown - Type generation workflow Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com> |
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@modelcontextprotocol/ext-apps
This repo contains the SDK and specification for MCP Apps Extension (SEP-1865).
MCP Apps are a proposed standard inspired by MCP-UI and OpenAI's Apps SDK to allow MCP Servers to display interactive UI elements in conversational MCP clients / chatbots.
How It Works
MCP Apps extend the Model Context Protocol to let servers deliver interactive UIs to MCP hosts. Here's how it works:
- Tool call — The LLM calls a tool on your server
- UI Resource — The tool's definition links to a predeclared
ui://resource containing its HTML interface - Host renders — The host fetches the resource and displays it in a sandboxed iframe
- Bidirectional communication — The host passes tool data to the UI via notifications, and the UI can call other tools through the host
This enables dashboards, forms, visualizations, and other rich experiences inside chat interfaces.
Overview
This SDK serves two audiences:
App Developers
Build interactive UIs that run inside MCP-enabled chat clients.
- SDK for Apps:
@modelcontextprotocol/ext-apps— API Docs - React hooks:
@modelcontextprotocol/ext-apps/react— API Docs
Host Developers
Embed and communicate with MCP Apps in your chat application.
- SDK for Hosts:
@modelcontextprotocol/ext-apps/app-bridge— API Docs
There's no supported host implementation in this repo (beyond the examples/basic-host example).
We have contributed a tentative implementation of hosting / iframing / sandboxing logic to the MCP-UI repository, and expect OSS clients may use it, while other clients might roll their own hosting logic.
Installation
npm install -S @modelcontextprotocol/ext-apps
Or edit your package.json manually:
{
"dependencies": {
"@modelcontextprotocol/ext-apps": "^0.0.1"
}
}
Examples
Start with these foundational examples to learn the SDK:
examples/basic-server-vanillajs— MCP server + MCP App using vanilla JSexamples/basic-server-react— MCP server + MCP App using Reactexamples/basic-server-vue— MCP server + MCP App using Vueexamples/basic-server-svelte— MCP server + MCP App using Svelteexamples/basic-server-preact— MCP server + MCP App using Preactexamples/basic-server-solid— MCP server + MCP App using Solidexamples/basic-host— MCP host application supporting MCP Apps
The examples/ directory contains additional demo apps showcasing real-world use cases.
To run all examples together:
npm install
npm start
Then open http://localhost:8080/.