What's mcp-ui? • Core Concepts • Installation • Getting Started • Walkthrough • Examples • Supported Hosts • Security • Roadmap • Contributing • License
mcp-ui pioneered the concept of interactive UI over MCP, enabling rich web interfaces for AI tools. Alongside Apps SDK, the patterns developed here directly influenced the MCP Apps specification, which standardized UI delivery over the protocol.
The @mcp-ui/* packages implement the MCP Apps standard. @mcp-ui/client is the recommended SDK for MCP Apps Hosts.
The @mcp-ui/ packages are fully compliant with the MCP Apps specification and ready for production use.*
mcpui.mp4
mcp-ui is an SDK implementing the MCP Apps standard for UI over MCP. It provides:
@mcp-ui/server(TypeScript): Create UI resources withcreateUIResource. Works withregisterAppToolandregisterAppResourcefrom@modelcontextprotocol/ext-apps/server.@mcp-ui/client(TypeScript): Render tool UIs withAppRenderer(MCP Apps) orUIResourceRenderer(legacy MCP-UI hosts).mcp_ui_server(Ruby): Create UI resources in Ruby.mcp-ui-server(Python): Create UI resources in Python.
The MCP Apps pattern links tools to their UIs via _meta.ui.resourceUri. Hosts fetch and render the UI alongside tool results.
The MCP Apps standard links tools to their UIs via _meta.ui.resourceUri:
import { registerAppTool, registerAppResource } from '@modelcontextprotocol/ext-apps/server';
import { createUIResource } from '@mcp-ui/server';
// 1. Create UI resource
const widgetUI = await createUIResource({
uri: 'ui://my-server/widget',
content: { type: 'rawHtml', htmlString: '<h1>Widget</h1>' },
encoding: 'text',
});
// 2. Register resource handler
registerAppResource(server, 'widget_ui', widgetUI.resource.uri, {}, async () => ({
contents: [widgetUI.resource]
}));
// 3. Register tool with _meta linking
registerAppTool(server, 'show_widget', {
description: 'Show widget',
inputSchema: { query: z.string() },
_meta: { ui: { resourceUri: widgetUI.resource.uri } } // Links tool → UI
}, async ({ query }) => {
return { content: [{ type: 'text', text: `Query: ${query}` }] };
});Hosts detect _meta.ui.resourceUri, fetch the UI via resources/read, and render it with AppRenderer.
The underlying payload for UI content:
interface UIResource {
type: 'resource';
resource: {
uri: string; // e.g., ui://component/id
mimeType: 'text/html;profile=mcp-app';
text?: string; // HTML content
blob?: string; // Base64-encoded HTML content
};
}uri: Unique identifier usingui://schememimeType:text/html;profile=mcp-app— the MCP Apps standard MIME typetextvs.blob: Plain text or Base64-encoded content
For MCP Apps hosts, use AppRenderer to render tool UIs:
import { AppRenderer } from '@mcp-ui/client';
function ToolUI({ client, toolName, toolInput, toolResult }) {
return (
<AppRenderer
client={client}
toolName={toolName}
sandbox={{ url: sandboxUrl }}
toolInput={toolInput}
toolResult={toolResult}
onOpenLink={async ({ url }) => window.open(url)}
onMessage={async (params) => console.log('Message:', params)}
/>
);
}Key props:
client: Optional MCP client for automatic resource fetchingtoolName: Tool name to render UI forsandbox: Sandbox configuration with proxy URLtoolInput/toolResult: Tool arguments and resultsonOpenLink/onMessage: Handlers for UI requests
For legacy hosts that embed resources in tool responses:
import { UIResourceRenderer } from '@mcp-ui/client';
<UIResourceRenderer
resource={mcpResource.resource}
onUIAction={(action) => console.log('Action:', action)}
/>Props:
resource: Resource object withuri,mimeType, and content (text/blob)onUIAction: Callback for handling tool, prompt, link, notify, and intent actions
Also available as a Web Component:
<ui-resource-renderer
resource='{ "mimeType": "text/html", "text": "<h2>Hello!</h2>" }'
></ui-resource-renderer>Rendered using the internal <HTMLResourceRenderer /> component, which displays content inside an <iframe>. This is suitable for self-contained HTML.
mimeType:text/html;profile=mcp-app(MCP Apps standard)
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.
MCP-UI SDKs includes adapter support for host-specific implementations, enabling your open MCP-UI widgets to work seamlessly regardless of host. Adapters automatically translate between MCP-UI's postMessage protocol and host-specific APIs. Over time, as hosts become compatible with the open spec, these adapters wouldn't be needed.
For Apps SDK environments (e.g., ChatGPT), this adapter translates MCP-UI protocol to Apps SDK API calls (e.g., window.openai).
How it Works:
- Intercepts MCP-UI
postMessagecalls from your widgets - Translates them to appropriate Apps SDK API calls
- Handles bidirectional communication (tools, prompts, state management)
- Works transparently - your existing MCP-UI code continues to work without changes
Usage:
import { createUIResource } from '@mcp-ui/server';
const htmlResource = await createUIResource({
uri: 'ui://greeting/1',
content: {
type: 'rawHtml',
htmlString: `
<button>
Call Tool
</button>
`
},
encoding: 'text',
});# 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/clientgem install mcp_ui_server# using pip
pip install mcp-ui-server
# or uv
uv add mcp-ui-serverYou can use GitMCP to give your IDE access to mcp-ui's latest documentation!
-
Server-side: Create a tool with UI using
_meta.ui.resourceUriimport { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'; import { registerAppTool, registerAppResource } from '@modelcontextprotocol/ext-apps/server'; import { createUIResource } from '@mcp-ui/server'; import { z } from 'zod'; const server = new McpServer({ name: 'my-server', version: '1.0.0' }); // Create UI resource const widgetUI = await createUIResource({ uri: 'ui://my-server/widget', content: { type: 'rawHtml', htmlString: '<h1>Interactive Widget</h1>' }, encoding: 'text', }); // Register resource handler registerAppResource(server, 'widget_ui', widgetUI.resource.uri, {}, async () => ({ contents: [widgetUI.resource] })); // Register tool with _meta linking registerAppTool(server, 'show_widget', { description: 'Show widget', inputSchema: { query: z.string() }, _meta: { ui: { resourceUri: widgetUI.resource.uri } } }, async ({ query }) => { return { content: [{ type: 'text', text: `Query: ${query}` }] }; });
-
Client-side: Render tool UIs with
AppRendererimport { AppRenderer } from '@mcp-ui/client'; function ToolUI({ client, toolName, toolInput, toolResult }) { return ( <AppRenderer client={client} toolName={toolName} sandbox={{ url: sandboxUrl }} toolInput={toolInput} toolResult={toolResult} onOpenLink={async ({ url }) => window.open(url)} onMessage={async (params) => console.log('Message:', params)} /> ); }
For hosts that don't support MCP Apps yet:
import { UIResourceRenderer } from '@mcp-ui/client';
<UIResourceRenderer
resource={mcpResource.resource}
onUIAction={(action) => console.log('Action:', action)}
/>Server-side: Build your UI resources
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