A2A vs MCP in 2025: Different Layers, Not Rivals
A lot of people still frame Agent2Agent (A2A) and Model Context Protocol (MCP) as if one has to win.
That’s the wrong model.
In practice, they solve different interoperability problems:
- MCP standardizes how an agent or model connects to tools, data, and external systems.
- A2A standardizes how one agent communicates and coordinates with another agent.
If you’re building serious agent systems in 2025, the useful question is not A2A or MCP?
It’s:
Where do I need tool interoperability, and where do I need agent interoperability?
The short version
Think of the stack like this:
MCP
Use MCP when your agent needs to:
- call SaaS tools
- access enterprise systems
- retrieve documents or live context
- expose a consistent tool interface across vendors
A2A
Use A2A when your system needs to:
- delegate tasks to other agents
- discover specialized agents
- exchange structured work state
- coordinate across teams, apps, or vendors
So the clean mental model is:
- MCP = agent ↔ tools/context
- A2A = agent ↔ agent
That’s complementary, not competitive.
What actually happened in 2025
1) Google launched A2A in April 2025
On April 9, 2025, Google announced the Agent2Agent Protocol, describing it as an open protocol for agents to communicate securely and coordinate actions across enterprise systems.
Google’s announcement explicitly said A2A was designed to complement Anthropic’s MCP, not replace it.
Google also said the launch had support from 50+ technology partners, including major enterprise and infrastructure players.
Source: Google Developers Blog, Announcing the Agent2Agent Protocol (A2A)
https://developers.googleblog.com/en/a2a-a-new-era-of-agent-interoperability/
2) A2A moved under Linux Foundation governance in June 2025
On June 23, 2025, the Linux Foundation announced the Agent2Agent Protocol Project, with A2A contributed by Google.
That matters because once a protocol moves into neutral governance, it becomes easier for the ecosystem to treat it as long-term infrastructure rather than one vendor’s experiment.
The Linux Foundation announcement also said support had grown to 100+ leading technology companies.
Source: Linux Foundation, Launches the Agent2Agent Protocol Project
https://www.linuxfoundation.org/press/linux-foundation-launches-the-agent2agent-protocol-project-to-enable-secure-intelligent-communication-between-ai-agents
3) OpenAI added MCP support in the Responses API in May 2025
On May 21, 2025, OpenAI announced support for remote MCP servers in the Responses API, building on earlier MCP support in the Agents SDK.
This is one of the strongest signals that MCP became real infrastructure, not just an idea from one vendor.
Source: OpenAI, New tools and features in the Responses API
https://openai.com/index/new-tools-and-features-in-the-responses-api/
4) Anthropic donated MCP to the Agentic AI Foundation in December 2025
On December 9, 2025, Anthropic announced it was donating MCP to the Agentic AI Foundation under the Linux Foundation.
Anthropic also shared adoption numbers that are hard to ignore:
- 10,000+ active public MCP servers
- adoption across ChatGPT, Cursor, Gemini, Microsoft Copilot, and VS Code
- growing cloud support from AWS, Cloudflare, Google Cloud, and Azure
That’s what protocol escape velocity looks like.
Source: Anthropic, Donating the Model Context Protocol and establishing the Agentic AI Foundation
https://www.anthropic.com/news/donating-the-model-context-protocol-and-establishing-of-the-agentic-ai-foundation
Why the confusion keeps happening
People confuse A2A and MCP because both are about interop.
But they sit at different layers.
MCP solves:
How does an agent reliably use external capabilities?
Examples:
- CRM access
- payments
- file systems
- internal APIs
- retrieval over company knowledge
A2A solves:
How does one agent ask another agent to do work, return results, and coordinate progress?
Examples:
- planner agent delegating to research agent
- support triage agent escalating to billing agent
- internal enterprise agents spanning different departments and vendors
This distinction matters because many “multi-agent” systems are actually just one agent with many tools. In that case, MCP may be enough.
But once you have specialized agents with separate responsibilities, policies, or runtime boundaries, A2A starts to make sense.
A practical architecture for builders
If I were designing an agent stack in 2025, I’d use this default:
Use MCP for the capability layer
- databases
- SaaS connectors
- search
- document systems
- internal APIs
Use A2A for the coordination layer
- agent discovery
- delegation
- task handoff
- status exchange
- cross-agent orchestration
That gives you a clean split:
- Agents use MCP to touch the world
- Agents use A2A to work with each other
That is a much healthier design than overloading one protocol to do everything.
My take
In 2025, MCP looks like the stronger tool-and-context standard.
The adoption evidence is broader and clearer.
But that does not make A2A irrelevant.
It means the market is clarifying the stack:
- MCP is becoming core infrastructure for connecting agents to real systems.
- A2A is the bet on standardized collaboration between independent agents.
So no, I don’t think the right headline is A2A vs MCP.
The right headline is:
MCP won the “tool connectivity” conversation early. A2A is trying to win the “agent collaboration” layer next.
If that framing holds, both matter.
The builder takeaway
If you’re shipping now:
- Don’t use A2A as a substitute for basic tool integration.
- Don’t force MCP to act like a full multi-agent coordination protocol.
- Start with the simplest architecture that matches your real problem.
In plain English:
- One agent, many tools? Start with MCP.
- Many agents, shared workflow? Add A2A.
- Enterprise-scale agent ecosystems? You probably want both.
That’s the stack.
If you’re building in this space, get the layer boundaries right early. It will save you a lot of pain later.
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