A Survey of Agent Interoperability Protocols: MCP, ACP, A2A, and ANP
Reference: Ehtesham, Singh, Gupta, Kumar (2025). arXiv:2505.02279. Source file: 2505.02279v1.pdf. URL
Summary
This survey examines four emerging agent communication protocols targeting different interoperability tiers: the Model Context Protocol (MCP) for JSON-RPC tool invocation and context delivery; the Agent Communication Protocol (ACP) for REST-native multi-part performative messaging; the Agent-to-Agent Protocol (A2A) for peer-to-peer Agent-Card-based task outsourcing; and the Agent Network Protocol (ANP) for decentralized discovery using DIDs and JSON-LD.
The authors contrast architectures, discovery mechanisms, security models, and communication patterns, then recommend a phased adoption roadmap (MCP for tool access, then ACP for messaging, A2A for collaborative execution, ANP for open marketplaces). A timeline traces ancestry from KQML (1993) and FIPA-ACL (2000) through RAG, ReAct, function-calling up to modern agent protocols.
Key Ideas
- Phased adoption roadmap: MCP -> ACP -> A2A -> ANP.
- MCP core primitives: Tools, Resources, Prompts, Sampling under JSON-RPC 2.0.
- A2A introduces Agent Cards, Tasks, Artifacts for enterprise-scale delegation.
- ANP uses DIDs and JSON-LD for decentralized, internet-scale agent discovery.
- Security threats tabulated across creation/operation/update lifecycle phases.
Connections
Conceptual Contribution
- Claim: Modern agent interoperability is best understood as a four-tier stack (MCP for tools, ACP for messaging, A2A for delegation, ANP for open discovery) and should be adopted in that phased order.
- Mechanism: Structured comparison of architectures, discovery, security, and message patterns; historical timeline rooting each protocol in KQML/FIPA-ACL ancestry; lifecycle threat table.
- Concepts introduced/used: Model Context Protocol, Agent-to-Agent Protocol, Agent Network Protocol, Agent Communication Protocol, KQML, FIPA-ACL, Agent Cards, Decentralized Identifiers, JSON-RPC, Tool Use, LLM Agents
- Stance: survey
- Relates to: Complements the broader Survey Of AI Agent Protocols with a narrower, adoption-oriented roadmap. Its security-threat lifecycle connects directly to AI Agents Under Threat and MalTool Malicious Tool Attacks.
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