Agent-to-agent protocol is a software communication standard that lets independent AI agents discover capabilities, delegate tasks, and exchange results. In AI, the term often refers to the open Agent2Agent (A2A) protocol, which supports structured, secure collaboration between agents without exposing their internal prompts or tools. It differs from a general API because it defines agent identity, task status, input, output, and handoffs.
Agent-to-Agent Protocol
What Is an Agent-to-Agent Protocol?
An agent-to-agent protocol is a software standard that lets independent AI agents discover capabilities, delegate tasks, and return results. Agent2Agent, or A2A, is a common open protocol for this collaboration.
How Agent-to-Agent Communication Works
- An agent finds another agent through capability metadata, often an agent card.
- It authenticates and checks permission for the requested task.
- It sends structured task inputs and receives a result, progress update, or clarification request.
- It validates the output before using it in a workflow.
Core Parts of an A2A Protocol
Core parts include identity, capability discovery, task objects, messages, artifacts, lifecycle states, streaming updates, and errors. Opaque agents can cooperate without exposing prompts, memory, model settings, or tool configuration.
A2A vs. MCP: What Is the Difference?
| Protocol | Connects | Example |
|---|---|---|
| A2A | Agent to agent | Delegate account research |
| MCP | Agent to tool or data | Query a database |
They can work together: an agent may use MCP tools while completing an A2A task.
Benefits of Agent-to-Agent Protocols
- Reusable specialist agents across frameworks.
- Clear task contracts and progress visibility.
- A support agent can ask a billing agent to retrieve approved account data.
Practical Limits and Security Controls
- A protocol does not guarantee accurate or safe agent behavior.
- Use authorization, minimal data sharing, validation, timeouts, idempotency keys, logs, and human approval for consequential actions.
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Frequently Asked Questions
Your Questions, Answered
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What is the A2A protocol and what is its purpose?
A2A is an open agent-to-agent protocol for discovering, authenticating, and coordinating independent AI agents. Its purpose is to make task delegation and result sharing more interoperable.
What is the agent-to-agent protocol and how does it work?
It defines a shared way for agents to advertise capabilities, receive structured tasks, report status, request clarification, and return outputs.
What are the key differences between MCP and A2A?
MCP usually connects an agent to tools, resources, or data. A2A connects one independent agent to another for task-based collaboration.
How do AI agents communicate with each other?
They use structured messages over network interfaces, with agreed schemas for identity, inputs, task state, results, errors, and access controls.
Is ChatGPT an agent or an LLM?
An LLM is a language model. ChatGPT is an AI application built around language models and may use agent-like capabilities when it can plan, use tools, and complete multi-step tasks.
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