MCP Apps
MCP Apps
Build interactive UIs for MCP tools — charts, forms, dashboards — that render inline in Claude, ChatGPT and any other compliant chat client.
Why<br>Quickstart<br>API Docs<br>Spec<br>Contributing
Excalidraw built with MCP Apps, running in Claude
Table of Contents
Build with Agent Skills
Supported Clients
Why MCP Apps?
How It Works
Getting Started
Using the SDK
Examples
Specification
Resources
Contributing
Build with Agent Skills
The fastest way to build an MCP App is to let your AI coding agent do it. This<br>repo ships four Agent Skills — install them once,<br>then just ask:
Skill<br>What it does<br>Try it
create-mcp-app<br>Scaffolds a new MCP App with an interactive UI from scratch<br>"Create an MCP App"
migrate-oai-app<br>Converts an existing OpenAI App to use MCP Apps<br>"Migrate from OpenAI Apps SDK"
add-app-to-server<br>Adds interactive UI to an existing MCP server's tools<br>"Add UI to my MCP server"
convert-web-app<br>Turns an existing web app into a hybrid web + MCP App<br>"Add MCP App support to my web app"
Install the Skills
Claude Code — install via the plugin marketplace:
/plugin marketplace add modelcontextprotocol/ext-apps<br>/plugin install mcp-apps@modelcontextprotocol-ext-apps<br>Copy
Other agents — any AI coding agent that supports<br>Agent Skills can use these skills. See the<br>agent skills guide for manual installation<br>instructions.
Once installed, verify by asking your agent "What skills do you have?" — you<br>should see create-mcp-app, migrate-oai-app, add-app-to-server, and<br>convert-web-app in the list. Then just ask it to create or migrate an app and<br>it will guide you through the rest.
Supported Clients
Note
MCP Apps is an extension to the<br>core MCP specification. Host<br>support varies — see the<br>clients page for the full list.
Why MCP Apps?
MCP tools return text and structured data. That works for many cases, but not<br>when you need an interactive UI, like a chart, form, design canvas or video player.
MCP Apps provide a standardized way to deliver interactive UIs from MCP servers.<br>Your UI renders inline in the conversation, in context, in any compliant host.
How It Works
MCP Apps extend the Model Context Protocol by letting tools declare UI<br>resources:
Tool definition — Your tool declares a ui:// resource containing its<br>HTML interface
Tool call — The LLM calls the tool on your server
Host renders — The host fetches the resource and displays it in a<br>sandboxed iframe
Bidirectional communication — The host passes tool data to the UI via<br>notifications, and the UI can call other tools through the host
Getting Started
npm install -S @modelcontextprotocol/ext-apps<br>Copy
New here? Start with the<br>Quickstart Guide<br>to build your first MCP App.
Using the SDK
The SDK serves three roles: app developers building interactive Views, host<br>developers embedding those Views, and MCP server authors registering tools with<br>UI metadata.
Package<br>Purpose<br>Docs
@modelcontextprotocol/ext-apps<br>Build interactive Views (App class, PostMessageTransport)<br>API Docs →
@modelcontextprotocol/ext-apps/react<br>React hooks for Views (useApp, useHostStyles, etc.)<br>API Docs →
@modelcontextprotocol/ext-apps/app-bridge<br>Embed and communicate with Views in your chat client<br>API Docs →
@modelcontextprotocol/ext-apps/server<br>Register tools and resources on your MCP server<br>API Docs →
There's no supported host implementation in this repo (beyond the<br>examples/basic-host<br>example).
The MCP-UI client SDK offers a<br>fully-featured MCP Apps framework used by a few hosts. Clients may choose to use<br>it or roll their own implementation.
Examples
The<br>examples/<br>directory contains demo apps showcasing real-world use cases.
Map<br>Three.js<br>ShaderToy
Sheet Music<br>Wiki Explorer<br>Cohort Heatmap
Scenario Modeler<br>Budget Allocator<br>Customer Segmentation
System Monitor<br>Transcript<br>Video Resource
PDF Server<br>QR Code (Python)<br>Say Demo
Starter Templates
The same app built with different frameworks — pick your favorite!
React · Vue · Svelte · Preact · Solid · Vanilla JS
Running the Examples
With basic-host
To run all examples locally using<br>basic-host<br>(the reference host implementation included in this repo):
git clone https://github.com/modelcontextprotocol/ext-apps.git<br>cd ext-apps<br>npm install<br>npm start<br>Copy
Then open http://localhost:8080/.
With MCP Clients
Every Node.js example is published as @modelcontextprotocol/server-. To<br>add one to an MCP client that supports stdio (Claude Desktop, VS Code, etc.),<br>use this pattern:
"mcpServers": {<br>"": {<br>"command": "npx",<br>"args": ["-y", "@modelcontextprotocol/server-", "--stdio"]<br>Copy
For example, to add the map server: @modelcontextprotocol/server-map. The<br>Python examples (qr-server, say-server) use uv run instead — see their<br>READMEs for details.
Local Development
To test local modifications with an MCP client, clone the repo, install, then<br>point your client at a local build:
"mcpServers": {<br>"": {<br>"command": "bash",<br>"args": [<br>"-c",<br>"cd ~/code/ext-apps/examples/-server && npm run build >&2 && node dist/index.js...