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75ecd62384* map-server: fix async/await in ontoolresult, remove unused getViewStorageKey * fix(map-server): improve updateModelContext and fix initialization - Use structured YAML frontmatter format for model context (like pdf-server) - Add tool name, altitude, and cleaner data format - Fix initialization deadlock: app.connect() was inside ontoolresult handler which could never fire until connected - Fix view state persistence: widgetUUID now properly extracted from ontoolresult and used to restore persisted camera position - Server now includes widgetUUID in tool result _meta for widget identification * fix(pdf-server): use widgetUUID for page persistence - Add widgetUUID to tool result _meta for widget identification - Use widgetUUID instead of generated key (pdfUrl+toolId) for localStorage - Enables reliable page restoration when revisiting PDF widgets * fix(transcript-server): use structured YAML frontmatter for model context - Add tool name, listening status, and unsent entry count in frontmatter - Consistent format with pdf-server and map-server * update names * drop bogus altitude * Update mcp-app.ts |
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@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.
How It Works
MCP Apps extend the Model Context Protocol to let servers deliver interactive UIs to MCP hosts. Here's how it works:
- Tool call — The LLM calls a tool on your server
- UI Resource — The tool's definition links to a predeclared
ui://resource containing its HTML interface - Host renders — The host fetches the resource and displays it in a sandboxed iframe
- Bidirectional communication — The host passes tool data to the UI via notifications, and the UI can call other tools through the host
This enables dashboards, forms, visualizations, and other rich experiences inside chat interfaces.
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
Or edit your package.json manually:
{
"dependencies": {
"@modelcontextprotocol/ext-apps": "^0.0.1"
}
}
Examples
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| Map | Three.js | ShaderToy |
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| Sheet Music | Wiki Explorer | Cohort Heatmap |
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| Scenario Modeler | Budget Allocator | Customer Segmentation |
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| System Monitor | Transcript | Video Resource |
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| PDF Server |
Starter Templates
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The same app built with different frameworks — pick your favorite! React · Vue · Svelte · Preact · Solid · Vanilla JS |
The examples/ directory contains additional demo apps showcasing real-world use cases.
To run all examples:
npm install
npm start
Then open http://localhost:8080/.