A2A vs MCP: What Each Agent Protocol Actually Does

MCP connects an agent to tools and data. A2A connects agents to each other. That one sentence clears up most of the confusion, but it does not tell you which of the two to build against first.

What MCP does

The Model Context Protocol is Anthropic open standard for the link between a model and everything outside it: files, databases, APIs, a local shell. You write an MCP server once, and any MCP aware client can use it.

Before it existed, every assistant needed a bespoke integration for every tool, which is why the same wiki connector got rebuilt several hundred times over. If you have ever wired a model into a ticketing system by hand, MCP is the layer you were reinventing.

What A2A does

Agent2Agent covers the other direction. It defines how agents built by different vendors, on different frameworks, discover each other, exchange messages and coordinate on a shared task.

Google announced it in April 2025 with backing from more than 100 technology companies, then handed the protocol, its specification and its SDKs to the Linux Foundation. The Linux Foundation launched the Agent2Agent Protocol Project on 23 June 2025, with vendor neutrality written in as a condition of the project.

A2A protocol vs MCP: which one you need

Both, eventually, but not in the same week. If your agent needs to read your data and call your services, that is MCP, and it is the first thing to get working. If you are running an open agent model on your own hardware, MCP is how it reaches your files without anything leaving the machine.

If you are building something that has to hand work to an agent you did not write and cannot inspect, that is A2A. The two do not overlap, which matters because plenty of early coverage framed them as a Google against Anthropic fight. An agent can speak MCP to its own tools and A2A to its peers inside the same request.

Why the governance is the real news

A protocol owned by the company that also sells the leading product can change whenever the product strategy changes. Moving A2A to a foundation removes that. It is the same thing that happened to HTTP and HTML: they stopped belonging to anyone in particular, and that is roughly when it became safe to build a business on top of them.

Neutral governance is worth more when the commercial layer keeps consolidating, as it did when Nvidia moved on Hugging Face. It also helps that agents which talk to each other are agents that can be talked into things, and agents have already found their way out of test environments. A neutral spec is easier to audit than a vendor one.

The part worth watching is adoption rather than specification. MCP spread because servers were quick to write and clients turned up fast. A2A has the governance and the company list. The open question is how many agents end up actually speaking it to each other, rather than declaring support and never placing a call.