OpenAI's Apps SDK enables third-party applications to integrate seamlessly within ChatGPT conversations, creating contextual experiences where users complete tasks without switching interfaces. The SDK applies Hick's Law and Fitts's Law principles to reduce decision complexity and interaction distance. Designers should focus on single-purpose, conversation-friendly tasks that can be summarized visually with minimal actions. Best practices include displaying only relevant information, limiting cards to two primary actions, and avoiding complex multi-step workflows. This shift positions ChatGPT as an operating system-like environment, expanding UX design scope toward flows, contexts, and systems that help AI communicate and align with human goals.