Capability · Comparison
A2A Protocol vs Anthropic MCP
A2A and MCP are both open protocols in the agentic AI stack but target different layers. A2A (Agent-to-Agent), originally from Google and now widely supported, defines how agents discover and communicate with other agents across organisational boundaries. MCP (Model Context Protocol), from Anthropic, defines how a single LLM consumes tools, resources, and prompts. They're usually used together: MCP inside an agent, A2A between agents.
Side-by-side
| Criterion | A2A Protocol | Anthropic MCP |
|---|---|---|
| Layer | Inter-agent (agent ↔ agent) | Intra-agent (LLM ↔ tool/resource) |
| Originator | Google, with broad industry adoption | Anthropic, with broad industry adoption |
| Primary primitives | Agent Cards, Tasks, Messages, Artifacts | Tools, Resources, Prompts, Sampling |
| Transport | HTTPS + JSON-RPC over SSE | stdio, HTTP/SSE, Streamable HTTP |
| Auth | OAuth 2.0 / OIDC | OAuth 2.1 for HTTP transport |
| Discovery | Agent Card (machine-readable capabilities) | Server capabilities at connect time |
| State model | Long-running tasks with lifecycle events | Session-oriented, request/response + streaming |
| Typical use | Enterprise agent marketplaces, agent mesh | IDEs, desktop apps, agent frameworks |
Verdict
A2A and MCP are complementary layers of a full agentic stack rather than alternatives. MCP lets a single agent safely use tools and resources; A2A lets many agents — often owned by different teams or organisations — discover each other, delegate tasks, and exchange results. Large agent deployments in 2026 commonly use MCP on the inside (to expose tools to the model) and A2A on the outside (to let the agent act as part of a broader multi-agent mesh).
When to choose each
Choose A2A Protocol if…
- You need agents from different teams or vendors to interoperate.
- Long-running cross-organisation tasks are part of your design.
- You want a standard Agent Card describing capabilities.
- You're building or joining an agent marketplace / mesh.
Choose Anthropic MCP if…
- You're building a single agent that needs tool and resource access.
- Your client is an IDE, desktop app, or chat interface.
- You want first-class support in Claude, Cursor, VS Code, etc.
- Your integrations are intra-organisation tool calls.
Frequently asked questions
Is A2A competing with MCP?
No. They sit at different levels of the stack — A2A is about agents talking to agents; MCP is about a single LLM talking to tools. Most real systems use both.
Can an MCP server be exposed as an A2A agent?
Yes — that's a common pattern. Wrap your MCP server in an A2A-speaking facade to let other agents consume it as a capability.
Which has broader adoption?
MCP exploded first (2024) and has the broader client ecosystem inside IDEs and desktop apps. A2A adoption is strongest in enterprise inter-agent scenarios and is growing.
Sources
- A2A Protocol — accessed 2026-04-20
- Model Context Protocol — accessed 2026-04-20