--- title: "MCP vs A2A | Agent MCP Directory" description: "MCP vs A2A: one sourced difference and a verdict for product engineers, platform leads and agent builders. Read 4 November 2026." canonical: https://agentmcpdirectory.com/compare/mcp-vs-a2a site: "Agent MCP Directory" last_updated: 2026-11-05 section: "Head-to-heads" --- # MCP vs A2A | Agent MCP Directory > MCP vs A2A: one sourced difference and a verdict for product engineers, platform leads and agent builders. Read 4 November 2026. Source: https://agentmcpdirectory.com/compare/mcp-vs-a2a Site: Agent MCP Directory Last reviewed: 2026-11-05 # MCP vs A2A Product engineer: Expose your product with MCP first; add A2A only if you ship an agent others delegate to. Developer-platform lead: Both now sit in the Agentic AI Foundation. Agent builder: Use MCP for tools and A2A for handing work to another agent. ## The sourced difference MCP connects an agent to tools, resources and prompts on a server; A2A connects agents to other agents through an Agent Card at /.well-known/agent-card.json and task messages over JSON-RPC, gRPC or HTTP+JSON. (MCP: [Model Context Protocol specification (latest, 2026-07-28)](https://modelcontextprotocol.io/specification/latest), read 5 November 2026; A2A: [A2A specification](https://a2a-protocol.org/latest/specification/), read 5 November 2026) ## Verdicts by reader | Reader | Verdict | | --- | --- | | Product engineer | Expose your product with MCP first; add A2A only if you ship an agent others delegate to. | | Developer-platform lead | Both now sit in the Agentic AI Foundation. | | Agent builder | Use MCP for tools and A2A for handing work to another agent. | ## Side by side | Aspect | MCP | A2A | | --- | --- | --- | | Maintainer | MCP maintainers under the Agentic AI Foundation | A2A project, Growth Stage project at the Agentic AI Foundation (Linux Foundation-directed) | | What it is | A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation. | A protocol for agents to discover each other through an Agent Card and exchange tasks and messages. | | Status and version | Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025. | Specification 1.0.0 is the latest release; joined the Agentic AI Foundation on 27 Aug 2026. | | What it does not do | Does not grade servers, verify registry entries, or prescribe a .well-known discovery file in the 2026-07-28 core spec; server cards are still Working Group work. | Does not define how an agent calls a plain API or a web page; it covers agent-to-agent tasks, not tool access. | Read the full entries: [MCP](https://agentmcpdirectory.com/standards/mcp/) and [A2A](https://agentmcpdirectory.com/standards/a2a/). ## Seen in the shared crawl | Path | Top 10,000 found | Ora leaderboard found | | --- | --- | --- | | /.well-known/mcp.json | 19 of 7,470 (0.25%) | 66 of 3,366 (1.96%) | A path counts only when the answer is the right kind of document. Many sites answer these paths with an ordinary web page, which is not counted. See [the census](https://agentmcpdirectory.com/census/). | Path | Top 10,000 found | Ora leaderboard found | | --- | --- | --- | | /.well-known/agent-card.json | 10 of 7,470 (0.13%) | 48 of 3,368 (1.43%) | | /.well-known/agent.json | 6 of 7,461 (0.08%) | 14 of 3,366 (0.42%) | Edition 4 November 2026 Method [How rows are verified](https://agentmcpdirectory.com/method/) Data [CSV and JSON](https://agentmcpdirectory.com/data/) Markdown [This page as markdown](https://agentmcpdirectory.com/compare/mcp-vs-a2a/index.md) ## Sources - [Model Context Protocol specification (latest, 2026-07-28)](https://modelcontextprotocol.io/specification/latest), read 5 November 2026 - [A2A specification](https://a2a-protocol.org/latest/specification/), read 5 November 2026 Last reviewed 5 November 2026