Agent interoperability concept

MCP versus A2A

Reference

MCP vs A2A: the Model Context Protocol (MCP, specification revision 2026-07-28) standardizes how an AI application connects to tools and data, while Agent2Agent (A2A, protocol version 1.0) standardizes communication between independent agents. Choose MCP when an agent needs capabilities or information from an external service; choose A2A when one agent needs to discover, delegate work to, or exchange results with another. They can also be used together.

Reviewed 2026-10-09

Two protocols for different connections

MCP (specification revision 2026-07-28) is a shared way for an AI application to connect with external systems such as tools and data sources. An MCP server makes capabilities available to a client; examples in the specification include resources, prompts, and tools.

A2A (protocol version 1.0) is a shared way for independent agent systems to communicate and collaborate. An agent can describe its identity and capabilities in an Agent Card, then exchange messages and manage tasks with another agent without exposing its internal tools or state.

The main difference is who is talking to whom

With MCP revision 2026-07-28, the connection is generally between an AI application and a service that provides tools, information, or prompts. The application can use those capabilities as part of its work. This is an integration between an agent and something it can use.

With A2A version 1.0, the connection is between independent agent systems. Its model includes messages, tasks, and artifacts, with options for streaming updates and task notifications. In plain terms, MCP describes a way to connect an agent to a capability; A2A describes a way for agents to coordinate work and pass results.

Choose by the connection you need

Use MCP revision 2026-07-28 when an AI application needs a standard connection to a tool, API, or data source. For example, a file search or database capability can be exposed for an application to call or consult.

Use A2A version 1.0 when a system needs to find or communicate with a separate agent, ask it to handle a task, and receive progress or a result. A2A describes agent discovery and task exchange, including messages, artifacts, and streaming or asynchronous updates. If a remote agent also needs tools or data, it can use MCP revision 2026-07-28 for those connections.

They can complement each other

A common mix-up is to treat MCP revision 2026-07-28 and A2A version 1.0 as competing ways to do the same job. Their official specifications describe different roles: MCP connects applications or agents with tools and external resources, while A2A connects independent agents.

They are not interchangeable labels for an API or an agent framework. A2A version 1.0 is a communication protocol, not a framework for building an agent; MCP revision 2026-07-28 standardizes connections to tools and data. One agent can receive a task over A2A and then use MCP to reach the tools or sources it needs.

Questions people ask

What is the difference between MCP and A2A?

MCP revision 2026-07-28 standardizes connections between AI applications and tools or data. A2A version 1.0 standardizes communication and task collaboration between independent agents.

Can an agent use MCP and A2A together?

Yes. An agent can communicate with another agent through A2A version 1.0 and use MCP revision 2026-07-28 to connect to its own tools, APIs, or data sources.

Does A2A tell an agent how to call its tools?

No. A2A version 1.0 handles communication between independent agents; its official project guide points to an agent's framework or MCP revision 2026-07-28 for tool calls.

What does an A2A Agent Card do?

In A2A version 1.0, an Agent Card is a JSON metadata document describing an agent's identity, capabilities, skills, endpoint, and authentication requirements.

Learn more

MCP specification, revision 2026-07-28
Read the formal MCP revision 2026-07-28 definitions for clients, servers, tools, resources, and prompts.
A2A Protocol Specification, version 1.0
See how A2A version 1.0 represents agent discovery, tasks, messages, and results.
How A2A Works with MCP
Read the A2A project's short explanation of how A2A version 1.0 and MCP revision 2026-07-28 can be used together.

What changed

Sources

Part of Agent interoperability: Four roles, four integration needs Match the interface to the user Check discovery and compatibility