A2A (Agent-to-Agent) is a protocol that was introduced by Google DeepMind in 2024 to standardize how autonomous AI agents communicate, collaborate, and share reasoning steps. It defines a structured message format and interaction model that lets agents exchange goals, tasks, and results securely — much like APIs did for application integration. A2A provides:
- Interoperability — A shared schema and ontology for multi-agent coordination, regardless of vendor or platform.
- Transparency — Message-level tracing for observability and audit.
- Scalability — Lightweight communication that supports swarms of cooperating agents.
- Security — Authentication and authorization across agent networks.
Originally developed for multi-agent reasoning experiments, A2A has since been implemented in open frameworks like LangChain, CrewAI, and Solace Platform, where it extends into enterprise-grade messaging and observability. Together, A2A and MCP form the nervous system of agentic systems — A2A for inter-agent dialogue, MCP for execution and external action.