What is it?
A useful picture: MCP is how an agent picks up tools; A2A is how agents talk to colleagues. A research agent might use MCP to read files and search the web, and A2A to ask a specialist agent from another company to analyse the data.
Also known as: MCP vs A2A, A2A versus MCP, Agent2Agent vs Model Context Protocol, do I need A2A and MCP, MCP or A2A, difference between MCP and A2A.
Technical definition
| MCP | A2A | |
|---|---|---|
| Connects | Host/client to server exposing tools, resources, prompts | Agent (client) to remote agent (server) |
| Unit of work | Tool call / resource read | Task with lifecycle, messages, artifacts |
| Remote party is | A capability provider | An autonomous agent with its own reasoning |
| Discovery | Capability listing after connection | Agent card describing skills |
| Typical trust concern | Tool poisoning, over-privileged tools (MCP Security Risks and Mitigations) | Untrusted agent output, delegation chains |
Specifications evolve; confirm details in current documents.
Entity type: concept · Freshness class: volatile.
When should I use it?
Use MCP by default for capabilities; add A2A for cross-agent delegation.
Implementation patterns
- Each agent uses MCP for its tools and A2A to delegate to peers.
- Orchestrator calls specialist agents via A2A; specialists call tools via MCP.
Technologies and frameworks
Commonly associated: MCP SDKs, A2A SDKs. Names are examples of what exists, not recommendations, and projects change quickly.
Practical guide
- Classify each remote capability as tool or agent.
- Implement MCP for tools.
- Add A2A where agents must interoperate.
- Secure both (MCP Security Risks and Mitigations).
Common failure modes
- Using A2A for what is really a tool call.
- Using MCP tools to emulate autonomous agents without lifecycle handling.
Troubleshooting
- Unsure which applies — If the remote side only executes a function, it is a tool (MCP); if it reasons and may take many steps, it is an agent (A2A).
Contrasted with
- What is MCP (Model Context Protocol)? — Tools and context.
- A2A (Agent2Agent) Protocol — Agent collaboration.
Questions this page answers
- What is the difference between A2A and MCP?
- Should I use MCP or A2A?
- Can MCP and A2A be used together?
- Does A2A replace MCP?
Typical goals: choose between MCP and A2A; combine both in an architecture.
Sources and verification
Status: not independently verified. This entry was authored on 2026-10-06 from general technical knowledge, without live checking of the sources below. Treat every source as a lead to confirm (identifier, title, authorship, current version) before publication or citation.
Freshness class: volatile — Products, versions, protocols, benchmarks, leaderboards, regulations and dates. Verify against the primary source before relying on specifics; re-review every 3 months.
Time-sensitive claims to verify before relying on them:
- Current versions and any overlap or convergence between the specifications.
Canonical sources (unverified leads):
- MCP specification — modelcontextprotocol.io
- A2A specification — a2a-protocol.org (verify)