A2A Protocol: How AI Agents Talk to Each Other
A2A (Agent-to-Agent) protocol is an emerging standard for direct communication between AI agents. While MCP handles how agents talk to tools and services, A2A handles how agents talk to each other — negotiating, delegating, and coordinating tasks. Google has been a major driver of A2A, pushing for an open standard that works across vendors and frameworks.
In This Guide
What Is A2A?
A2A (Agent-to-Agent) protocol is an emerging standard for direct communication between AI agents. While MCP handles how agents talk to tools and services, A2A handles how agents talk to each other.
As multi-agent systems become the norm, standardizing agent communication becomes critical. Without A2A, every multi-agent system invents its own coordination protocol — leading to fragmentation and interoperability issues.
Google has been a major driver of A2A, pushing for an open standard that works across vendors and frameworks — similar to how MCP evolved into an open standard under the Linux Foundation.
MCP
Agent → Tools & Services
Vertical integration
A2A
Agent ↔ Agent
Horizontal coordination
MCP vs A2A
| Aspect | MCP | A2A |
|---|---|---|
| Purpose | Agent-to-tool communication | Agent-to-agent communication |
| Use Case | Using databases, APIs, browsers | Delegating tasks, coordinating work |
| Direction | Agent → External service | Agent ↔ Agent |
| Maturity | Widely adopted (Linux Foundation) | Emerging standard |
They Work Together
MCP and A2A are complementary. An orchestrator agent might use A2A to delegate a task to a specialist agent, which then uses MCP to access the tools needed to complete that task. Both protocols are essential for sophisticated multi-agent systems.
A2A Use Cases
Task Delegation
Agent A assigns subtasks to specialized Agent B and receives results
Verification Requests
Code agent asks review agent to validate changes before proceeding
Capability Discovery
Orchestrator queries available agents to find who can handle a task
Status Coordination
Agents report progress and coordinate handoffs in pipelines
Resource Negotiation
Agents negotiate access to shared resources or exclusive locks
Consensus Building
Multiple agents vote or reach agreement on decisions
Frequently Asked Questions
What is A2A Protocol?
A2A (Agent-to-Agent) protocol is an emerging standard for direct communication between AI agents. While MCP handles agent-to-tool communication, A2A standardizes how agents talk to each other - negotiating, delegating, and coordinating tasks.
How is A2A different from MCP?
MCP (Model Context Protocol) lets agents use tools and access data. A2A lets agents communicate with other agents. They're complementary - an agent might use MCP to access a database and A2A to coordinate with a review agent.
Who is backing A2A?
Google has been a major driver of A2A, alongside other industry players. The goal is an open standard that works across vendors, similar to how MCP became an open standard under the Linux Foundation.
Why do agents need to talk to each other?
Multi-agent systems require coordination. One agent might need to delegate a subtask, request verification, or negotiate a decision. A2A provides structured patterns for these interactions rather than ad-hoc solutions.
What can agents communicate via A2A?
Task delegation and results, capability discovery (what can you do?), resource negotiation, status updates, verification requests, and coordination messages. It's designed for the full lifecycle of multi-agent collaboration.
Is A2A production-ready?
A2A is still emerging. While MCP has become a de facto standard, A2A adoption is earlier. Teams building multi-agent systems should track the standard and design with compatibility in mind.
How do A2A and MCP work together?
They're the two layers of agent communication: MCP for agent-to-tool (vertical integration) and A2A for agent-to-agent (horizontal coordination). Together they enable sophisticated multi-agent architectures.
Can you help with A2A implementation?
Yes. We help teams design multi-agent architectures that leverage both MCP and emerging A2A patterns. This includes agent coordination, message design, and building systems ready for protocol evolution.
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