A2UI

A2UI is an open-source declarative protocol that enables AI agents to generate rich, native user interfaces through structured JSON rather than plain text or executable code.

A2UI (Agent-to-User Interface) standardizes how autonomous agents communicate visual intent to front-end applications. Developed by Google with contributions from the open-source community, the protocol uses a streaming JSON format to describe UI components (cards, lists, and forms) that are rendered natively by host frameworks like Flutter, Angular, and Lit. By separating the agent's reasoning from the client's rendering, A2UI ensures security across trust boundaries (no arbitrary code execution) while maintaining visual consistency with the application's existing design system. Version 0.9 introduces client-defined functions and cross-platform syncing, allowing developers to build sophisticated, agent-driven tools that feel like integrated software rather than simple chatbots.

https://a2ui.org