A2A Explained: The Agent-to-Agent Protocol

A2A, the Agent-to-Agent protocol, is an open standard for AI agents to communicate and delegate tasks to one another. It originated at Google and, since 17 August 2026, is a hosted project of the Agentic AI Foundation, the Linux Foundation body that also holds MCP. In the context of agentic commerce it is best understood as a coordination layer: it is not a commerce protocol in itself, but the substrate that buyer and merchant agents use to talk, and that payment standards build on.

Where it stands

The mechanism is an agent card: a structured description of what an agent can do and how to reach it, which an agent publishes and other agents read to discover capabilities and delegate work without a human brokering the handoff. A2A reached v1.0, its first stable specification, in March 2026, adding multi-protocol bindings and version negotiation, enterprise multi-tenancy, signed agent cards for cryptographic identity verification, and a migration path for early adopters. At the protocol’s one-year mark in April 2026 the Linux Foundation reported more than 150 supporting organizations, up from around 50 a year earlier, including AWS, Cisco, Google, IBM, Microsoft, Salesforce, SAP, and ServiceNow, with the protocol embedded in Azure AI Foundry, Copilot Studio, and Amazon Bedrock AgentCore.

Who governs it, and why the August move matters

A2A launched at Google in April 2025 and was donated to the Linux Foundation the same year. On 17 August 2026 it moved again, out of the Linux Foundation’s broader portfolio and into the Agentic AI Foundation (AAIF) as a hosted project, alongside MCP, Block’s goose, AGENTS.md, and agentgateway. Each project keeps its own maintainers, specification process, and release cadence.

The practical significance is narrow but real. The two protocols agentic commerce leans on most, MCP for tool and data access and A2A for agent-to-agent coordination, are now governed in the same place under the same neutral structure. That removes a category of vendor risk for anyone building multi-agent systems, and it is the clearest instance so far of the pattern the rest of 2026 has followed: standards moving out of their sponsors and into neutral bodies. What it does not do is change the specification, the maintainers, or anything a builder integrates against today.

The Linux Foundation is explicit that A2A and MCP are complementary rather than competing: A2A defines how agents communicate and coordinate across organizational boundaries, while MCP defines how an agent connects to tools and data sources. Now that both sit under AAIF, that division of labor is a governance position as well as a technical one.

Its role in commerce

A2A shows up underneath the payment layer rather than at the checkout. Two connections matter. First, AP2, the payment-authorization standard, is designed to be used as an extension of A2A (and of MCP), so the signed-mandate machinery can ride on top of agent-to-agent messaging. Second, an A2A x402 extension brings x402-style stablecoin payments to agent-to-agent interactions, built by Google with Coinbase, the Ethereum Foundation, and MetaMask. In both cases A2A handles how the agents coordinate, and the commerce or payment specifics live in an extension on top.

How to hold it in your head

Keep the layers separate: A2A is how agents talk and delegate, MCP is how an agent discovers tools, and the commerce and payment protocols (ACP, UCP, AP2, x402, MPP) run the actual transaction on top. A2A is the most behind-the-scenes of the agentic commerce acronyms, which is why it usually appears as a foundation other protocols extend rather than something a merchant integrates directly. For the full map, see the protocol stack.

FAQ

What is A2A? An open standard for agents to communicate and delegate to one another, originated at Google, donated to the Linux Foundation in 2025, and a hosted project of the Agentic AI Foundation since 17 August 2026. Its first stable specification, v1.0, shipped in March 2026, and more than 150 organizations support it. It is a coordination layer, not a commerce protocol.

Who governs A2A? The Agentic AI Foundation, a Linux Foundation body, as of 17 August 2026. It sits there alongside MCP, goose, AGENTS.md, and agentgateway, which puts agent coordination and tool access under the same neutral governance.

What does it have to do with agentic commerce? It is the substrate payment extensions build on: AP2 is designed to be used as an A2A extension (and as an MCP extension), and an A2A x402 extension adds stablecoin payments. A2A handles agent coordination; commerce rides on top.

Is A2A a payment protocol? No. Payments ride on top of A2A through extensions like AP2 and the A2A x402 extension, rather than being part of A2A itself.