## Ranking of Agentic Web Protocols in the Order of Importance

Here’s our take, focusing on protocols that actually make a “web of agents” work (interop first, then tools, then plumbing):

1. **A2A (Agent-to-Agent Protocol)** — the backbone of multi-agent interoperability: lets independently built agents discover each other, exchange tasks/results, and coordinate securely across vendors. Without A2A, you don’t really have a *web* of agents. ([Google Developers Blog][1], [A2A Protocol][2], [Google Cloud][3])

2. **MCP (Model Context Protocol)** — the de-facto standard for agent-to-tool/data access: a “USB-C for AI” that standardizes how agents discover and call tools, files, and data sources. It’s what turns reasoning into action. ([Anthropic][4], [Model Context Protocol][5], [Anthropic][6], [The Verge][7])

3. **ACP (Agent Communication Protocol)** — an A2A-style alternative with Linux Foundation governance and a growing ecosystem (BeeAI). Important as a parallel, production-minded path to agent interop. ([IBM Research][8], [agentcommunicationprotocol.dev][9], [linuxfoundation.org][10])

4. **JSON Schema/JSON RPC (for capability description & tool contracts)** — not agent-specific, but still the lingua franca most agent protocols lean on for describing functions and payloads consistently. (Commonly referenced in A2A/MCP docs and implementations.) ([The Register][11])

5. **OAuth 2.0 / OIDC (for auth & identity between agents/services)** — the practical security layer most real deployments ride on for trust, consent, and scoped access when agents call tools or other agents. (Explicitly surfaced in A2A guidance for secure interop.) ([Google Cloud][3])

If you want a “pure agentic” reading, #1–#3 are the core; #4–#5 are the essential web plumbing you’ll end up using to ship anything real. Also: the recent Agentic Web overview paper highlights A2A/MCP as *the* primary comms stack for this era. ([arXiv][12])

[1]: https://developers.googleblog.com/en/a2a-a-new-era-of-agent-interoperability/?utm_source=chatgpt.com "Announcing the Agent2Agent Protocol (A2A)"
[2]: https://a2aprotocol.ai/?utm_source=chatgpt.com "A2A Protocol - Agent2Agent Communication"
[3]: https://cloud.google.com/products/agent-builder?utm_source=chatgpt.com "Vertex AI Agent Builder"
[4]: https://www.anthropic.com/news/model-context-protocol?utm_source=chatgpt.com "Introducing the Model Context Protocol"
[5]: https://modelcontextprotocol.io/?utm_source=chatgpt.com "Model Context Protocol"
[6]: https://docs.anthropic.com/en/docs/mcp?utm_source=chatgpt.com "Model Context Protocol (MCP)"
[7]: https://www.theverge.com/2024/11/25/24305774/anthropic-model-context-protocol-data-sources?utm_source=chatgpt.com "Anthropic launches tool to connect AI systems directly to datasets"
[8]: https://research.ibm.com/projects/agent-communication-protocol?utm_source=chatgpt.com "Agent Communication Protocol (ACP)"
[9]: https://agentcommunicationprotocol.dev/?utm_source=chatgpt.com "Agent Communication Protocol: Welcome"
[10]: https://www.linuxfoundation.org/press/ai-workflows-get-new-open-source-tools-to-advance-document-intelligence-data-quality-and-decentralized-ai-with-ibms-contribution-of-3-projects-to-linux-fou-1745937200621?utm_source=chatgpt.com "AI Workflows Get New Open Source Tools to Advance ..."
[11]: https://www.theregister.com/2025/07/12/ai_agent_protocols_mcp_a2a/?utm_source=chatgpt.com "MCP vs A2A: Agentic AI protocols take shape"
[12]: https://arxiv.org/abs/2507.21206?utm_source=chatgpt.com "Agentic Web: Weaving the Next Web with AI Agents"