Interactive UI rendered inside ChatGPT or Claude — OpenAI Apps SDK apps, MCP Apps (the @modelcontextprotocol/ext-apps standard), or MCP-UI components, with a Next.js/React server. Covers the MCP tool and resource architecture, the window.openai / ui-bridge data flow, widget state, sandbox/CSP security, display modes, visual design, and directory submission. Trigger when building, reviewing, or designing such apps — even when the user only says "chat app", "ChatGPT widget", "Claude app", "render UI in chat", "window.openai", "createUIResource", "outputTemplate", or "MCP app UI" without naming a specific SDK.
This skill does not declare a tool allowlist. The agent host applies whatever default tools are available at runtime.
SKILL.md / Manifest
https://raw.githubusercontent.com/pproenca/dot-skills/master/skills/.experimental/chat-apps-ui-sdk/SKILL.mdRegistry
github (via claudemarketplaces.com)