A2UI is an open-source protocol developed by Google that enables AI agents to generate secure, interactive user interfaces across web, mobile, and desktop platforms without executing arbitrary code. By utilizing declarative component descriptions, A2UI allows agents to communicate UI structures that client applications render using native components, ensuring a seamless and secure user experience. Key Features and Functionality: - Security by Design: A2UI employs a declarative data format, eliminating the need for executable code. Agents are restricted to using pre-approved components from a defined catalog, mitigating risks associated with UI injection attacks. - LLM-Friendly Format: The protocol utilizes a flat, streaming JSON structure optimized for large language models (LLMs), facilitating incremental UI generation without requiring perfect JSON output in a single instance. - Framework Agnostic: A2UI's design ensures compatibility across various frameworks, allowing the same agent response to be rendered on platforms such as Angular, Flutter, React, or native mobile applications using the client's styled components. - Progressive Rendering: The protocol supports streaming UI updates as they are generated, enabling users to observe the interface being built in real-time, enhancing the overall user experience. Primary Value and User Solutions: A2UI addresses the challenge of safely transmitting rich, interactive UIs from AI agents across trust boundaries. Traditional methods often rely on text-only responses or the execution of potentially unsafe code. A2UI offers a secure alternative by allowing agents to send declarative component descriptions that clients render using their native widgets. This approach ensures that AI-generated interfaces are both secure and native to the platform, providing users with a consistent and trustworthy experience. By implementing A2UI, developers can enhance the capabilities of AI agents, enabling them to present complex information and gather structured input through dynamic, interactive interfaces, all while maintaining security and platform compatibility.