This walks you through building interactive UIs that run inside Claude Desktop and other MCP hosts. The core pattern is simple: register a tool that returns data, link it to an HTML resource that displays the UI, and the host handles the rendering. You get framework templates for React, Vue, Svelte, and vanilla JS, plus the patterns doc covers real stuff like chunked responses, polling dashboards, and streaming input. The gotchas are predictable: register handlers before calling connect, always configure CSP for network requests since there's no same origin server, and don't forget text fallbacks for hosts without UI support. If you're adding interactive views to MCP tools, this is the reference you clone and adapt from.
npx skills add https://github.com/modelcontextprotocol/ext-apps --skill create-mcp-app