MCP, A2A, and AG-UI ↗
yesEditorial Notes
AG-UI occupies the UI layer of the emerging agentic stack, handling how agents stream state and actions to frontend applications — contrast this with MCP (which standardizes tool access) and A2A (which handles agent-to-agent communication). Understanding this three-protocol landscape is essential before building any production agent system, because choosing the wrong integration point leads to brittle architectures. Pay close attention to how AG-UI’s event-driven model differs from traditional request-response patterns, and note that AG-UI is designed to be backend-agnostic, so it works regardless of which LLM provider or agent framework you choose.
Original Documentation
Documentation Index#
Fetch the complete documentation index at: https://docs.ag-ui.com/llms.txt Use this file to discover all available pages before exploring further.
Understanding how AG-UI complements and works with MCP and A2A
Agentic Protocols#
The agentic ecosystem is rapidly organizing around a family of open, complementary protocols — each addressing a distinct layer of interaction. AG-UI has emerged as the 3rd leg of the AI protocol landscape:
You can connect your application to agents directly via AG-UI, MCP, and A2A.
MCP (Model Context Protocol) Connects agents to tools and to context — but those tools are themselves becoming agentic.
A2A (Agent to Agent) Connects agents to other agents.
AG-UI (Agent–User Interaction) Connects agents to users (through user-facing applications).
You can think of AG-UI as the “kitchen sink” protocol — informed by bottom-up, real-world needs for building best-in-class agentic applications.
These three agentic protocols are complementary and have distinct technical goals; a single agent can and often does use all 3 simultaneously.
AG-UI Handshakes with MCP and A2A#
AG-UI contributors have recently added handshakes, allowing AG-UI to “front for” agents through MCP and A2A protocols, which allows AG-UI client apps and libraries to seamlessly use MCP and A2A supporting agents.
AG-UI’s mandate is to support the full set of building blocks required by modern agentic applications.
Generative UI Specs#
Recently several generative ui specs (including MCP-UI, Open JSON UI, and A2UI) have been released which allow agents to deliver UI widgets through the interaction protocols. AG-UI works with all of these. Visit our generative ui specs page to lern more.