MCP vs A2A: tools for agents vs agents talking to agents
MCP connects an agent to tools and data; A2A (Agent2Agent) lets independent agents discover each other and delegate tasks.
Short answer
MCP is about an agent using tools and data sources. A2A (the Agent2Agent protocol) is about one agent handing a task to another agent that may run elsewhere and be built with a different framework.
Who is behind A2A
A2A was originally developed by Google and donated to the Linux Foundation. It is maintained by a Technical Steering Committee with representatives from companies including AWS, Cisco, Google, IBM Research, Microsoft, Salesforce, SAP and ServiceNow, and is licensed under Apache 2.0.
Complementary, not competing
The A2A project itself describes the two as complementary: MCP standardises agent-to-tool communication, A2A standardises agent-to-agent communication. A typical system uses both: agents delegate work to each other over A2A, and each agent uses MCP servers for its own tools (for example a GitHub repository or a SQL database). A2A is not a tool-call protocol and does not replace MCP.
Which one do you need?
- Your assistant needs to read a database, call an API or drive a browser: MCP.
- You run several specialised agents, possibly from different vendors or frameworks, that must hand tasks to each other: A2A, with MCP inside each agent.
Source: a2a-protocol.org.