The author explores A2UI, an emerging protocol for building agentic interfaces, aiming to explain its implementation for developers. A2UI enables AI agents to dynamically generate interactive user interfaces across web, mobile, and desktop without arbitrary code execution, facilitating seamless and portable experiences. Unlike a framework, A2UI is a protocol that defines communication between an LLM agent and a client application, allowing developers to use their preferred frontend technology for rendering. The core architecture involves a server-side agent generating a UI layout message based on a shared schema, and a client-side application interpreting and rendering that message.On the server (agent) side, developers must provide several key inputs: a catalog of available UI building blocks (ranging from basic elements to custom components defined in JSON Schema), a natural language UI description guiding the agent on when and how to use specific UIs, and few-shot examples to illustrate the desired JSON message structure. Additionally, developers can augment UI descriptions with "agent skills" to define specific user capabilities and use cases, and "action mappings" to handle user interactions by translating events into new natural language queries for the agent. Agent tools, while a general agentic concept, are also crucial for performing tasks like fetching data or interacting with APIs.On the client side, particularly in an Angular application, the primary non-boilerplate requirement is configuring the application to render the components defined in the server-side catalog. If only standard elements are used, a basic catalog suffices. However, if the agent generates custom components, the client needs corresponding Angular implementations and a custom catalog that extends the basic one to register these components. A crucial rule is that the client's component definitions must perfectly match the catalog schemas and examples provided to the agent, ensuring accurate rendering of the dynamically generated UI.