@postman/mcp-ui-client

📦 Model Context Protocol UI SDK

What's mcp-ui? • Core Concepts • Installation • Getting Started • Walkthrough • Examples • Security • Roadmap • Contributing • License

mcp-ui brings interactive web components to the Model Context Protocol (MCP). Deliver rich, dynamic UI resources directly from your MCP server to be rendered by the client. Take AI interaction to the next level!

This project is an experimental community playground for MCP UI ideas. Expect rapid iteration and enhancements!

💡 What's mcp-ui?

mcp-ui is a collection of SDKs comprising:

• @mcp-ui/server (TypeScript): Utilities to generate UI resources (UIResource) on your MCP server.
• @mcp-ui/client (TypeScript): UI components (e.g., <UIResourceRenderer />) to render the UI resources and handle their events.
• mcp_ui_server (Ruby): Utilities to generate UI resources on your MCP server in a Ruby environment.

Together, they let you define reusable UI snippets on the server side, seamlessly and securely render them in the client, and react to their actions in the MCP host environment.

✨ Core Concepts

In essence, by using mcp-ui SDKs, servers and hosts can agree on contracts that enable them to create and render interactive UI snippets (as a path to a standardized UI approach in MCP).

UI Resource

The primary payload returned from the server to the client is the UIResource:

interface UIResource {
  type: 'resource';
  resource: {
    uri: string;       // e.g., ui://component/id
    mimeType: 'text/html' | 'text/uri-list' | 'application/vnd.mcp-ui.remote-dom'; // text/html for HTML content, text/uri-list for URL content, application/vnd.mcp-ui.remote-dom for remote-dom content (Javascript)
    text?: string;      // Inline HTML, external URL, or remote-dom script
    blob?: string;      // Base64-encoded HTML, URL, or remote-dom script
  };
}

• uri: Unique identifier for caching and routing
  • ui://… — UI resources (rendering method determined by mimeType)
• mimeType: text/html for HTML content (iframe srcDoc), text/uri-list for URL content (iframe src), application/vnd.mcp-ui.remote-dom for remote-dom content (Javascript)
  • MCP-UI requires a single URL: While text/uri-list format supports multiple URLs, MCP-UI uses only the first valid http/s URL and warns if additional URLs are found
• text vs. blob: Choose text for simple strings; use blob for larger or encoded content.

Resource Renderer

The UI Resource is rendered in the <UIResourceRenderer /> component. It automatically detects the resource type and renders the appropriate component.

It accepts the following props:

• resource: The resource object from an MCP Tool response. It must include uri, mimeType, and content (text, blob)
• onUIAction: Optional callback for handling UI actions from the resource:

  { type: 'tool', payload: { toolName: string, params: Record<string, unknown> }, messageId?: string } |
  { type: 'intent', payload: { intent: string, params: Record<string, unknown> }, messageId?: string } |
  { type: 'prompt', payload: { prompt: string }, messageId?: string } |
  { type: 'notify', payload: { message: string }, messageId?: string } |
  { type: 'link', payload: { url: string }, messageId?: string }
  

  When actions include a messageId, the iframe automatically receives response messages for asynchronous handling.
• supportedContentTypes: Optional array to restrict which content types are allowed (['rawHtml', 'externalUrl', 'remoteDom'])
• htmlProps: Optional props for the internal <HTMLResourceRenderer>
  • style: Optional custom styles for the iframe
  • iframeProps: Optional props passed to the iframe element
• remoteDomProps: Optional props for the internal <RemoteDOMResourceRenderer>
  • library: Optional component library for Remote DOM resources (defaults to basicComponentLibrary)
  • remoteElements: remote element definitions for Remote DOM resources.

Supported Resource Types

HTML (text/html and text/uri-list)

Rendered using the internal <HTMLResourceRenderer /> component, which displays content inside an <iframe>. This is suitable for self-contained HTML or embedding external apps.

• mimeType:
  • text/html: Renders inline HTML content.
  • text/uri-list: Renders an external URL. MCP-UI uses the first valid http/s URL.

Remote DOM (application/vnd.mcp-ui.remote-dom)

Rendered using the internal <RemoteDOMResourceRenderer /> component, which utilizes Shopify's remote-dom. The server responds with a script that describes the UI and events. On the host, the script is securely rendered in a sandboxed iframe, and the UI changes are communicated to the host in JSON, where they're rendered using the host's component library. This is more flexible than iframes and allows for UIs that match the host's look-and-feel.

• mimeType: application/vnd.mcp-ui.remote-dom+javascript; framework={react | webcomponents}

UI Action

UI snippets must be able to interact with the agent. In mcp-ui, this is done by hooking into events sent from the UI snippet and reacting to them in the host (see onUIAction prop). For example, an HTML may trigger a tool call when a button is clicked by sending an event which will be caught handled by the client.

🏗️ Installation

TypeScript

# using npm
npm install @mcp-ui/server @mcp-ui/client

# or pnpm
pnpm add @mcp-ui/server @mcp-ui/client

# or yarn
yarn add @mcp-ui/server @mcp-ui/client

Ruby

gem install mcp_ui_server

🚀 Getting Started

You can use GitMCP to give your IDE access to mcp-ui's latest documentation!

TypeScript

• Server-side: Build your UI resources

  import { createUIResource } from '@mcp-ui/server';
  import {
   createRemoteComponent,
   createRemoteDocument,
   createRemoteText,
  } from '@remote-dom/core';
  
  // Inline HTML
  const htmlResource = createUIResource({
    uri: 'ui://greeting/1',
    content: { type: 'rawHtml', htmlString: '<p>Hello, MCP UI!</p>' },
    encoding: 'text',
  });
  
  // External URL
  const externalUrlResource = createUIResource({
    uri: 'ui://greeting/1',
    content: { type: 'externalUrl', iframeUrl: 'https://example.com' },
    encoding: 'text',
  });
  
  // remote-dom
  const remoteDomResource = createUIResource({
    uri: 'ui://remote-component/action-button',
    content: {
      type: 'remoteDom',
      script: `
       const button = document.createElement('ui-button');
       button.setAttribute('label', 'Click me for a tool call!');
       button.addEventListener('press', () => {
         window.parent.postMessage({ type: 'tool', payload: { toolName: 'uiInteraction', params: { action: 'button-click', from: 'remote-dom' } } }, '*');
       });
       root.appendChild(button);
       `,
      framework: 'react', // or 'webcomponents'
    },
    encoding: 'text',
  });
  

• Client-side: Render in your MCP host

  import React from 'react';
  import { UIResourceRenderer } from '@mcp-ui/client';
  
  function App({ mcpResource }) {
    if (
      mcpResource.type === 'resource' &&
      mcpResource.resource.uri?.startsWith('ui://')
    ) {
      return (
        <UIResourceRenderer
          resource={mcpResource.resource}
          onUIAction={(result) => {
            console.log('Action:', result);
          }}
        />
      );
    }
    return <p>Unsupported resource</p>;
  }
  

Ruby

Server-side: Build your UI resources

require 'mcp_ui_server'

# Inline HTML
html_resource = McpUiServer.create_ui_resource(
  uri: 'ui://greeting/1',
  content: { type: :raw_html, htmlString: '<p>Hello, from Ruby!</p>' },
  encoding: :text
)

# External URL
external_url_resource = McpUiServer.create_ui_resource(
  uri: 'ui://greeting/2',
  content: { type: :external_url, iframeUrl: 'https://example.com' },
  encoding: :text
)

# remote-dom
remote_dom_resource = McpUiServer.create_ui_resource(
  uri: 'ui://remote-component/action-button',
  content: {
    type: :remote_dom,
    script: "
     const button = document.createElement('ui-button');
     button.setAttribute('label', 'Click me from Ruby!');
     button.addEventListener('press', () => {
       window.parent.postMessage({ type: 'tool', payload: { toolName: 'uiInteraction', params: { action: 'button-click', from: 'ruby-remote-dom' } } }, '*');
     });
     root.appendChild(button);
     ",
    framework: :react,
  },
  encoding: :text
)

🚶 Walkthrough

For a detailed, simple, step-by-step guide on how to integrate mcp-ui into your own server, check out the full server walkthroughs on the mcp-ui documentation site:

• TypeScript Server Walkthrough
• Ruby Server Walkthrough

These guides will show you how to add a mcp-ui endpoint to an existing server, create tools that return UI resources, and test your setup with the ui-inspector!

🌍 Examples

Client Examples

• ui-inspector - inspect local mcp-ui-enabled servers.
• MCP-UI Chat - interactive chat built with the mcp-ui client. Check out the hosted version!
• MCP-UI RemoteDOM Playground (examples/remote-dom-demo) - local demo app to test RemoteDOM resources (intended for hosts)

Server Examples

• TypeScript: A full-featured server that is deployed to a hosted environment for easy testing.
  • typescript-server-demo: A simple Typescript server that demonstrates how to generate UI resources.
  • server: A full-featured Typescript server that is deployed to a hosted Cloudflare environment for easy testing.
    • HTTP Streaming: https://remote-mcp-server-authless.idosalomon.workers.dev/mcp
    • SSE: https://remote-mcp-server-authless.idosalomon.workers.dev/sse
• Ruby: A barebones demo server that shows how to use mcp_ui_server and mcp gems together.

Drop those URLs into any MCP-compatible host to see mcp-ui in action. For a supported local inspector, see the ui-inspector.

🔒 Security

Host and user security is one of mcp-ui's primary concerns. In all content types, the remote code is executed in a sandboxed iframe.

🛣️ Roadmap

• Add online playground
• Expand UI Action API (beyond tool calls)
• Support Web Components
• Support Remote-DOM
• Add component libraries (in progress)
• Add SDKs for additional programming languages (in progress; Ruby available)
• Support additional frontend frameworks
• Add declarative UI content type
• Support generative UI?

🤝 Contributing

Contributions, ideas, and bug reports are welcome! See the contribution guidelines to get started.

📄 License

Apache License 2.0 © The MCP-UI Authors

Disclaimer

This project is provided "as is", without warranty of any kind. The mcp-ui authors and contributors shall not be held liable for any damages, losses, or issues arising from the use of this software. Use at your own risk.