---
title: "A2UI"
description: "A2UI is a JSON-based streaming protocol for agent-generated user interfaces. It lets an agent describe UI surfaces, components, data models, updates, and renderer-to-agent events in a structured stream that a compatible renderer can validate and display."
canonical_url: "https://promptmetheus.com/resources/llm-knowledge-base/a2ui"
---

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A2UI is a JSON-based streaming protocol for agent-generated user interfaces. It lets an agent describe UI surfaces, components, data models, updates, and renderer-to-agent events in a structured stream that a compatible renderer can validate and display.

A2UI is part of the broader [generative UI](https://promptmetheus.com/resources/llm-knowledge-base/generative-ui) ecosystem. Instead of sending only Markdown or prose, an agent can progressively create and update interactive UI elements. This is useful for dashboards, forms, multi-step workflows, approval screens, and rich task outputs.

The protocol separates several concerns:

- the agent emits component and data-model updates;
- the renderer validates and displays the UI;
- user actions are sent back to the agent through event messages; and
- transport bindings can map A2UI over systems such as [AG-UI](https://promptmetheus.com/resources/llm-knowledge-base/agent-user-interaction-protocol-ag-ui), [A2A](https://promptmetheus.com/resources/llm-knowledge-base/agent2agent-protocol-a2a), or [MCP](https://promptmetheus.com/resources/llm-knowledge-base/model-context-protocol-mcp).

A2UI should not give a model arbitrary control over a frontend. Renderers need component allowlists, schema validation, event constraints, permission checks, and clear provenance so users understand which agent produced the interface.

The [A2UI v1.0 candidate specification](https://github.com/a2ui-project/a2ui/blob/main/specification/v1_0/docs/a2ui_protocol.md) describes A2UI as a JSON streaming protocol for dynamically rendering agent-provided user interfaces.

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