Ext Apps

<!-- LOGO --> <div align="center"> <img src="media/mcp.svg#gh-light-mode-only" alt="MCP Apps" width="128"> <img src="media/mcp-white.svg#gh-dark-mode-only" alt="MCP Apps" width="128"> <h1>MCP Apps</h1> <p> Build interactive UIs for MCP tools — charts, forms, dashboards — that render inline in Claude, ChatGPT and any other compliant chat client. <br /><br /> <a href="#why-mcp-apps">Why</a> · <a href="https://apps.extensions.modelcontextprotocol.io/api/documents/Quickstart.html">Quickstart</a> · <a href="https://apps.extensions.modelcontextprotocol.io/api/">API Docs</a> · <a href="https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx">Spec</a> · <a href="CONTRIBUTING.md">Contributing</a> </p> </div> <p align="center"> <a href="https://github.com/modelcontextprotocol/ext-apps/actions/workflows/ci.yml"><img src="https://github.com/modelcontextprotocol/ext-apps/actions/workflows/ci.yml/badge.svg" alt="CI"></a> <a href="LICENSE"><img src="https://img.shields.io/badge/license-Apache%202.0-blue" alt="License: Apache 2.0"></a> <a href="https://www.npmjs.com/package/@modelcontextprotocol/ext-apps"><img src="https://img.shields.io/npm/v/@modelcontextprotocol/ext-apps.svg" alt="npm version"></a> <a href="https://www.npmjs.com/package/@modelcontextprotocol/ext-apps"><img src="https://img.shields.io/npm/dm/@modelcontextprotocol/ext-apps.svg" alt="npm downloads"></a> <a href="https://github.com/modelcontextprotocol/ext-apps"><img src="https://img.shields.io/github/stars/modelcontextprotocol/ext-apps" alt="GitHub stars"></a> <a href="https://apps.extensions.modelcontextprotocol.io/api/"><img src="https://img.shields.io/badge/docs-API%20Reference-blue" alt="API Documentation"></a> </p> <p align="center"> <img src="media/excalidraw.gif" alt="MCP Apps demo" width="600"> <br><em>Excalidraw built with MCP Apps, running in Claude</em> </p> ## Table of Contents - [Build with Agent Skills](#build-with-agent-skills) - [Supported Clients](#supported-clients) - [Why MCP Apps?](#why-mcp-apps) - [How It Works](#how-it-works) - [Getting Started](#getting-started) - [Using the SDK](#using-the-sdk) - [Examples](#examples) - [Specification](#specification) - [Resources](#resources) - [Contributing](#contributing) ## Build with Agent Skills The fastest way to build an MCP App is to let your AI coding agent do it. This repo ships four [Agent Skills](https://agentskills.io/) — install them once, then just ask: | Skill | What it does | Try it | | --------------------------------------------------------------------------- | ----------------------------------------------------------- | ------------------------------------- | | [`create-mcp-app`](./plugins/mcp-apps/skills/create-mcp-app/SKILL.md) | Scaffolds a new MCP App with an interactive UI from scratch | _"Create an MCP App"_ | | [`migrate-oai-app`](./plugins/mcp-apps/skills/migrate-oai-app/SKILL.md) | Converts an existing OpenAI App to use MCP Apps | _"Migrate from OpenAI Apps SDK"_ | | [`add-app-to-server`](./plugins/mcp-apps/skills/add-app-to-server/SKILL.md) | Adds interactive UI to an existing MCP server's tools | _"Add UI to my MCP server"_ | | [`convert-web-app`](./plugins/mcp-apps/skills/convert-web-app/SKILL.md) | Turns an existing web app into a hybrid web + MCP App | _"Add MCP App support to my web app"_ | ### Install the Skills **Claude Code** — install via the plugin marketplace: ``` /plugin marketplace add modelcontextprotocol/ext-apps /plugin install mcp-apps@modelcontextprotocol-ext-apps ``` **Other agents** — any AI coding agent that supports [Agent Skills](https://agentskills.io/) can use these skills. See the [agent skills guide](./docs/agent-skills.md) for manual installation instructions. Once installed, verify by asking your agent _"What skills do you have?"_ — you should see `create-mcp-app`, `migrate-oai-app`, `add-app-to-server`, and `convert-web-app` in the list. Then just ask it to create or migrate an app and it will guide you through the rest. ## Supported Clients <p align="center"> <a href="https://developers.openai.com/apps-sdk/mcp-apps-in-chatgpt/"><img src="https://img.shields.io/badge/ChatGPT-docs-74aa9c?logo=openai&logoColor=white" alt="ChatGPT"></a> <a href="https://claude.com/docs/connectors/building/mcp-apps/getting-started"><img src="https://img.shields.io/badge/Claude-docs-d97706?logo=claude&logoColor=white" alt="Claude"></a> <a href="https://code.visualstudio.com/blogs/2026/01/26/mcp-apps-support"><img src="https://img.shields.io/badge/VS_Code-docs-007ACC?logo=visualstudiocode&logoColor=white" alt="VS Code"></a> <a href="https://block.github.io/goose/docs/tutorials/building-mcp-apps/"><img src="https://img.shields.io/badge/Goose-docs-000000?logo=goose&logoColor=white" alt="Goose"></a> <a href="https://learning.postman.com/docs/postman-ai/mcp-requests/interact"><img src="https://img.shields.io/badge/Postman-docs-FF6C37?logo=postman&logoColor=white" alt="Postman"></a> <a href="https://www.mcpjam.com/blog/mcp-apps-example"><img src="https://img.shields.io/badge/MCPJam-docs-8B5CF6" alt="MCPJam"></a> </p> > [!NOTE] > MCP Apps is an extension to the > [core MCP specification](https://modelcontextprotocol.io/specification). Host > support varies — see the > [clients page](https://modelcontextprotocol.io/clients) for the full list. ## Why MCP Apps? MCP tools return text and structured data. That works for many cases, but not 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. 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 resources: 1. **Tool definition** — Your tool declares a `ui://` resource containing its HTML interface 2. **Tool call** — The LLM calls the tool on your server 3. **Host renders** — The host fetches the resource and displays it in a sandboxed iframe 4. **Bidirectional communication** — The host passes tool data to the UI via notifications, and the UI can call other tools through the host ## Getting Started ```bash npm install -S @modelcontextprotocol/ext-apps ``` **New here?** Start with the [Quickstart Guide](https://apps.extensions.modelcontextprotocol.io/api/documents/Quickstart.html) to build your first MCP App. ## Using the SDK The SDK serves three roles: app developers building interactive Views, host developers embedding those Views, and MCP server authors registering tools with UI metadata. | Package | Purpose | Docs | | ------------------------------------------- | --------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------- | | `@modelcontextprotocol/ext-apps` | Build interactive Views (App class, PostMessageTransport) | [API Docs →](https://apps.extensions.modelcontextprotocol.io/api/modules/app.html) | | `@modelcontextprotocol/ext-apps/react` | React hooks for Views (useApp, useHostStyles, etc.) | [API Docs →](https://apps.extensions.modelcontextprotocol.io/api/modules/_modelcontextprotocol_ext-apps_react.html) | | `@modelcontextprotocol/ext-apps/app-bridge` | Embed and communicate with Views in your chat client | [API Docs →](https://apps.extensions.modelcontextprotocol.io/api/modules/app-bridge.html) | | `@modelcontextprotocol/ext-apps/server` | Register tools and resources on your MCP server | [API Docs →](https://apps.extensions.modelcontextprotocol.io/api/modules/server.html) | There's no _supported_ host implementation in this repo (beyond the [examples/basic-host](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-host) example). The [MCP-UI](https://github.com/idosal/mcp-ui) client SDK offers a fully-featured MCP Apps framework used by a few hosts. Clients may choose to use it or roll their own implementation. ## Examples The [`examples/`](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples) directory contains demo apps showcasing real-world use cases. <!-- prettier-ignore-start --> | | | | |:---:|:---:|:---:| | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/map-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/threejs-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/shadertoy-server) | | [**Map**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/map-server) | [**Three.js**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/threejs-server) | [**ShaderToy**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/shadertoy-server) | | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/sheet-music-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/wiki-explorer-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/cohort-heatmap-server) | | [**Sheet Music**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/sheet-music-server) | [**Wiki Explorer**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/wiki-explorer-server) | [**Cohort Heatmap**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/cohort-heatmap-server) | | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/scenario-modeler-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/budget-allocator-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/customer-segmentation-server) | | [**Scenario Modeler**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/scenario-modeler-server) | [**Budget Allocator**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/budget-allocator-server) | [**Customer Segmentation**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/customer-segmentation-server) | | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/system-monitor-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/transcript-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/video-resource-server) | | [**System Monitor**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/system-monitor-server) | [**Transcript**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/transcript-server) | [**Video Resource**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/video-resource-server) | | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/pdf-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/qr-server) | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/say-server) | | [**PDF Server**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/pdf-server) | [**QR Code (Python)**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/qr-server) | [**Say Demo**](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/say-server) | ### Starter Templates | | | |:---:|:---| | [](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-react) | The same app built with different frameworks — pick your favorite!<br><br>[React](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-react) · [Vue](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-vue) · [Svelte](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-svelte) · [Preact](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-preact) · [Solid](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-solid) · [Vanilla JS](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-server-vanillajs) | <!-- prettier-ignore-end --> ### Running the Examples #### With basic-host To run all examples locally using [basic-host](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-host) (the reference host implementation included in this repo): ```bash git clone https://github.com/modelcontextprotocol/ext-apps.git cd ext-apps npm install npm start ``` Then open http://localhost:8080/. #### With MCP Clients Every Node.js example is published as `@modelcontextprotocol/server-<name>`. To add one to an MCP client that supports stdio (Claude Desktop, VS Code, etc.), use this pattern: ```json { "mcpServers": { "<name>": { "command": "npx", "args": ["-y", "@modelcontextprotocol/server-<name>", "--stdio"] } } } ``` For example, to add the map server: `@modelcontextprotocol/server-map`. The Python examples (`qr-server`, `say-server`) use `uv run` instead — see their READMEs for details. #### Local Development To test local modifications with an MCP client, clone the repo, install, then point your client at a local build: ```json { "mcpServers": { "<name>": { "command": "bash", "args": [ "-c", "cd ~/code/ext-apps/examples/<name>-server && npm run build >&2 && node dist/index.js --stdio" ] } } } ``` ## Specification <div align="center"> | Version | Status | Link | | -------------- | ----------- | --------------------------------------------------------------------------------------------------------------------------------- | | **2026-01-26** | Stable | [specification/2026-01-26/apps.mdx](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx) | | **draft** | Development | [specification/draft/apps.mdx](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/draft/apps.mdx) | </div> ## Resources - [Quickstart Guide](https://apps.extensions.modelcontextprotocol.io/api/documents/Quickstart.html) - [API Documentation](https://apps.extensions.modelcontextprotocol.io/api/) - [Specification (2026-01-26)](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx) ([Draft](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/draft/apps.mdx)) - [SEP-1865 Discussion](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1865) ## Contributing Contributions are welcome! Please read [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines on how to get started, submit pull requests, and report issues.