@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.

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
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Or edit your package.json manually:

{
  "dependencies": {
    "@modelcontextprotocol/ext-apps": "^0.0.1"
  }
}
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Examples

Start with these foundational examples to learn the SDK:

• examples/basic-server-vanillajs — Example MCP server with tools that return UI Apps (vanilla JS)
• examples/basic-server-react — Example MCP server with tools that return UI Apps (React)
• examples/basic-host — Bare-bones example of hosting MCP Apps

The examples/ directory contains additional demo apps showcasing real-world use cases.

To run all examples together:

npm install
npm run examples:start
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Then open http://localhost:8080/.

Resources

• Quickstart Guide
• API Documentation
• Draft Specification
• SEP-1865 Discussion