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//how agents communicate

AI agent communication protocol

AI agents need to communicate — with the tools they use, with other agents, and with the apps that call them. This guide explains how AI agent communication works today and which protocols standardise each part.

Beginner-friendly

How do AI agents communicate?

An AI agent is a system that uses a model to pursue a goal over multiple steps — planning, calling tools and acting, rather than answering a single prompt. To do useful work it must communicate beyond its own process: reading data, invoking tools, and sometimes coordinating with other agents.

Early on, each of those connections was hand-built. Communication protocols replace that bespoke wiring with shared conventions, so an agent can talk to many tools and peers through one consistent interface.

Three kinds of AI agent communication

  1. Using tools and data. The agent calls functions and reads resources. The Model Context Protocol (MCP) standardises this.
  2. Talking to other agents. The agent delegates a sub-task to a specialised peer. Agent2Agent (A2A) standardises this.
  3. Being driven by a client. An application starts and monitors the agent through an API. The Agent Protocol REST spec standardises this.
A worked example
A support agent receives a ticket via an API (client-to-agent), looks up the customer in a database through MCP (agent-to-tool), and asks a billing agent to issue a refund over A2A (agent-to-agent). Three layers, three protocols, one task.

What makes agent communication reliable

  • Structured messages — predictable formats both sides can parse.
  • Capability discovery — learning what a tool or agent offers at runtime.
  • Task tracking — starting, monitoring and completing long-running work.
  • Clear errors — consistent handling when something fails.

Where the standards are heading

This is a fast-moving area and no single standard covers everything. The pragmatic approach is to understand the layers, pick the protocol that fits the connection in front of you, and keep an eye on how the specs evolve. The agent communication protocol page covers the same ground with a slightly more technical framing.

//questions

Frequently asked questions

What protocol do AI agents use to communicate?

There isn't one universal protocol. The most common are MCP (agent-to-tool), A2A (agent-to-agent) and the Agent Protocol REST spec (client-to-agent). Which one applies depends on what the agent is communicating with.

Can agents from different companies talk to each other?

That's the goal of interoperability standards like A2A: an agent advertises its capabilities via an agent card, and another agent can discover and delegate to it without shared code. Support is still maturing, so test before relying on it.

Is this the same as an agent communication protocol?

Yes — 'AI agent communication protocol' and 'agent communication protocol' refer to the same idea. We keep both pages because readers search for both phrasings.

// AgentProtocol is independent and not the official source for any protocol named here.