MCP solved tool calling. A2A solved coordination. What solves transport?
Why this matters: a development in AI with implications for how people work, create, and decide.
The history of distributed computing is one of protocol proliferation followed by consolidation. Common Object Request Broker Architecture (CORBA), Distributed Component Object Model (DCOM), Java remote method invocation (RMI), and early simple object access protocol (SOAP) competed for the enterprise integration market in the late 1990s before representational state transfer (REST) quietly won by being simpler and HTTP-native. Extensible Messaging and Presence Protocol (XMPP), Internet Relay Chat (IRC), and a dozen proprietary protocols fragmented real-time messaging before MG telemetry transport (MQTT) and WebSockets carved out their respective niches. Every new computing paradigm generates a burst of competing standards, then slowly converges as implementations accumulate and interoperability becomes economically necessary.The AI agent ecosystem is currently in the proliferation phase. Four significant protocols have been published in the past eighteen months: Model context protocol (MCP) from Anthropic in late 2024, agent communication protocol (ACP) from IBM Research in March 2025, Agent2Agent (A2A) from Google in April 2025, and agent network protocol (ANP) from an independent working group. The W3C AI Agent Protocol Community Group has opened a standards track. The Internet Engineering Task Force (IETF) is receiving Internet-Drafts on agent transport. Conferences are running workshops on interoperability. Every week brings a new GitHub repository claiming to solve the agent communication problem.Understanding where and how quickly this converges has real consequences for architecture decisions being made right now.What the protocols actually solveThe proliferation looks more chaotic than it is, because most of these protocols address different layers of a stack rather than competing for the same slot. The confusion comes from marketing, which describes each as "the standard for AI agent communication" without specifying which aspect of communication.MCP is a