The ext-apps repository is the official specification and SDK for the MCP Apps protocol, a standard that enables interactive user interfaces to be embedded within AI chatbots served by Model Context Protocol servers. Written primarily in TypeScript, the project provides a comprehensive framework for building and deploying interactive UIs such as charts, forms, dashboards, and design canvases that render inline within Claude, ChatGPT, VS Code, and other compliant chat clients.
The repository serves three distinct audiences through its modular SDK packages. App developers use the core @modelcontextprotocol/ext-apps package and its React hooks to build interactive Views with bidirectional communication capabilities. Host developers leverage the app-bridge package to embed and communicate with these Views within their chat clients. MCP server authors use the server package to register tools and resources with UI metadata on their MCP servers. The protocol extends the core Model Context Protocol by allowing tools to declare UI resources via ui:// references, which hosts then fetch and display in sandboxed iframes while maintaining bidirectional communication between the interface and the underlying tools.
The project includes four Agent Skills designed to accelerate development: create-mcp-app scaffolds new applications from scratch, migrate-oai-app converts existing OpenAI Apps to use MCP Apps, add-app-to-server adds interactive UI to existing MCP server tools, and convert-web-app transforms existing web applications into hybrid web plus MCP App implementations. These skills integrate with Claude Code and other AI coding agents that support the Agent Skills framework, allowing developers to request app creation or migration through natural language prompts.
According to GitGenius activity tracking across 134 issues and pull requests, the repository demonstrates strong engagement with a median response latency of zero hours and a mean response latency of 62.3 hours. The most active issue labels are enhancement with 44 items and bug with 43 items, indicating ongoing feature development and quality improvements. The protocol label appears on 7 items, reflecting discussions about specification changes. Primary contributors idosal, ochafik, and liady have driven 93, 79, and 41 tracked events respectively, establishing a core team actively maintaining the project. The repository shares overlapping contributors with holoviz/panel, microsoft/vscode, and storybookjs/storybook, suggesting cross-pollination with established UI and development tool ecosystems.
The repository provides comprehensive documentation including a quickstart guide, full API reference, and detailed specification. The examples directory contains demo applications showcasing real-world use cases. While the repository does not include a fully-featured host implementation beyond a basic example, the MCP-UI client SDK offers a complete framework used by several hosts. The project is licensed under Apache 2.0 and published to npm, with CI workflows ensuring code quality and stability.
