Notes on MCP and A2A

You have almost certainly met it as a war. MCP versus A2A. Which protocol wins, which to bet on, which is about to make the other obsolete. This episode dismantles that framing, because the question is broken, not subtle. In the middle of August 2026 the two supposed rivals quietly moved into the same house, both now governed by the same neutral foundation. That is the tell. First, the wider frame: system integration. For thirty years the central problem in enterprise software was not intelligence, it was getting one system to talk to another, and the quiet enabler was the API, a published contract built for a human programmer who reads the docs and writes exact code at build time. Agents broke that assumption, because the thing calling the tool is now a probabilistic model deciding at run time. Which lets us confront the sharp objection head on: is MCP just a sexier way to call an API? At the wire, often yes, an MCP connector wraps an API that already existed. But the reader changed. An API describes itself to a human once, in documentation; an MCP tool describes itself to a model every time, so an agent can discover and use it on the spot, with no one having written code for that exact combination in advance. Same items, completely different reader, and the reader was always the point. We get precise about what each one actually is. MCP, the Model Context Protocol, born at Anthropic in November 2024, is the vertical: a single common way for an agent to reach down to its tools and data, a USB C port for AI. In about a year it went from an internal idea to a de facto standard adopted by OpenAI, Google and Microsoft, with a public registry of thousands of connectors, and was then donated to a neutral foundation. A2A, the Agent to Agent protocol, born at Google in April 2025, is the horizontal: how one agent reaches sideways to another, across organizational boundaries, using a signed agent card that lets machines discover, understand and hand off work to each other with no human brokering the introduction. So the versus dissolves. MCP is the worker picking up a tool. A2A is the worker talking to a colleague. Two floors of the same building, not two horses in a race. Then the strange part, and the reason this matters. A2A does not just let an agent use tools. It lets an agent hire other agents. Delegate to a counterparty it did not build, does not own, and may never have met. That is a change in kind. It turns using software into transacting with strangers, at machine speed, with almost none of the scaffolding that human commerce spent centuries building. We follow the thread to the agent to agent economy: self assembling supply chains of machines, the trust problem underneath (why the first thing A2A reached for was cryptographically signed identity), and the accountability question no one has cleanly answered yet, when something three hops down a chain of agents goes wrong. The honest read: the plumbing is arriving fast and it is good. The answer to the human question underneath is not arriving at the same speed. When an agent can act, and now also transact, delegate and hire, the old comfort that a person is always in the loop stops being automatically true. You have to put them there on purpose. No hype. No horse race. Narrated by a synthetic voice, on purpose. A podcast from Vesster.