What Is A2A? The Agent2Agent Protocol Explained

A2A (Agent2Agent) is an open protocol that standardizes how AI agents communicate with each other. Created by Google and announced in April 2025, it solves a simple but critical problem: agents built by different teams on different frameworks can't see each other's capabilities. Without a shared language, every agent-to-agent integration becomes a bespoke engineering project. A2A gives them that language — a standard way to discover what another agent can do, hand it a task, and track the result.

Think of it this way: if MCP is the USB-C port that plugs an agent into its tools, A2A is the phone network that lets agents call each other. One handles the vertical connection (agent → tools and data); the other handles the horizontal one (agent → agent).

How A2A works

Agent cards: discovery

Every A2A agent publishes an "agent card" — a standardized description of its identity, capabilities, and how to reach it. Before delegating, an agent reads the card to learn what the other agent offers, much like reading a business card before starting a conversation. This makes capability discovery automatic instead of requiring pre-negotiated integrations.

Tasks: delegation with tracking

Work is exchanged as tasks with a lifecycle: created, in progress, awaiting input, completed. When your agent hands a goal to another agent — say, a travel agent asking a booking agent to hold flights — it gets back a tracked task, not just a fire-and-forget message. Either side can stream updates, request clarification, or pause for human approval mid-task.

Framework independence

The protocol doesn't care what an agent is built with. An agent on one framework can delegate to an agent on another, because both speak A2A at the boundary while keeping their internals — prompts, tools, models — private. That privacy boundary matters: you can expose what your agent does without exposing how.

A2A vs. MCP: complementary, not competing

This is the single most misunderstood point, so let's be explicit:

• MCP = how an agent reaches tools and data. One agent, many capabilities.
• A2A = how agents reach each other. Many agents, coordinated work.

A mature multi-agent deployment uses both: A2A for a coordinator agent to delegate a reconciliation task to a specialist agent, MCP for each agent to reach the databases and APIs it needs. Neither replaces the other, and neither replaces your existing REST APIs — which remain the deterministic contract for system-to-system integration while agents handle the judgment-heavy work alongside them.

Governance: why it matters

Protocols live or die on trust, and trust here means neutrality. Google donated A2A to the Linux Foundation in June 2025, and since August 2026 it has been a hosted project of the Agentic AI Foundation — the same Linux Foundation body that governs MCP. That puts the two most important agent standards under one vendor-neutral roof, backed by the major cloud providers and model labs.

For buyers, the practical takeaway: agent interoperability is no longer an experiment. When evaluating agents for multi-vendor environments, open-protocol support (A2A for agent-to-agent, MCP for tool connectivity) is a meaningful signal that the product is built for an interoperable future rather than a walled garden.

Do you need to care about A2A?

Probably not directly. A2A is infrastructure — like TCP/IP, you benefit from it without configuring it. It matters to:

• Vendors building agents that must interoperate across platforms.
• Enterprises running multi-agent systems from multiple providers.
• Buyers only insofar as protocol support signals a product's openness — one checkbox among many in the buying framework.

What reaches you is the outcome: agents from different vendors that can actually work together, instead of an archipelago of incompatible silos. See AI agent use cases for where multi-agent coordination is already paying off.