A survey of agent interoperability protocols: Model Context Protocol (MCP), Agent Communication Protocol (ACP), Agent-to-Agent Protocol (A2A), and Agent Network Protocol (ANP)

This survey characterizes and compares four agent interoperability protocols (MCP, ACP, A2A, ANP) across interaction modes, discovery mechanisms, communication patterns, and security models. MCP provides JSON-RPC client–server tool invocation; ACP offers REST-based multimodal messaging; A2A enables P2P peer delegation via Agent Cards; ANP supports decentralized DID-based open-internet collaboration. A phased adoption roadmap is proposed sequencing MCP > ACP > A2A > ANP.