What is the difference between A2A and MCP?

They govern different edges of the system. MCP standardizes how an agent reaches the tools, data, and context it consumes — edges run agent-to-server. A2A standardizes how one agent asks another agent to take on work — edges run agent-to-agent. They compose rather than substitute, and a mature estate will want both.

Should I build on A2A now or wait?

Coordinate through MCP today — it is the protocol most agents already speak and it is enough to let many agents share one piece of work through a shared context server. Treat A2A as a forward path: adopt its direct-delegation patterns as they stabilize, layered onto the same shared context, ownership, and conflict model you already run.

What is A2A (agent-to-agent), and how does it relate to MCP?

A plain explanation of agent-to-agent communication, the boundary it standardizes, and why it complements MCP rather than competing with it.

By Quordo · Published 2026-06-18 · Updated 2026-06-18 · 6 min read

Key takeaways

A2A (agent-to-agent) is an emerging approach for autonomous agents to discover, delegate to, and negotiate with each other directly — the sideways edge between agent peers.
A2A and MCP are complementary, not competing: MCP connects an agent to tools and context (agent-to-server), A2A connects an agent to other agents (agent-to-agent).
The pragmatic stance for platform teams is to coordinate through MCP today and treat A2A as a roadmap path as those patterns stabilize.

What A2A actually is

A2A, short for agent-to-agent, is an emerging approach for autonomous agents to discover, delegate to, and negotiate with each other directly, rather than only through a human or a shared backend. Where a single agent calls tools and reasons on its own, A2A addresses the case where one agent needs another agent to do something it cannot: find a peer that advertises a capability it lacks, hand off a task with the context required to complete it, and receive a result and status back in a shape it can use. The mechanics it standardizes are concrete — how an agent publishes what it can do, how a request is framed, and how the response and progress flow back — so that agents from different teams or vendors can act as a callable network rather than isolated endpoints.

The problem A2A targets is specific. As organizations deploy more agents, work increasingly spans more than one of them: a research agent produces findings that an analysis agent should act on, a planning agent decomposes a goal into tasks that specialist agents execute. Today that stitching is mostly bespoke — each connection is hand-built, brittle when either side changes, and impossible to reuse. That is the same N-times-M integration problem standards exist to collapse, applied to the agent-to-agent edge specifically. A2A is the attempt to make an agent able to delegate to a peer it was never explicitly wired to, as long as both speak the protocol.

It is worth being precise about scope, because the term is used loosely. A2A is concerned with the interaction between agents as peers: capability advertisement, task delegation, and the exchange of results and status between independent agents. It is not a coordination system on its own — it says nothing about who holds the source of truth, which agent owns a piece of work, or how to detect that two agents have conflicted — and it is not yet a single converged standard the way more established protocols are. Treating A2A as a maturing pattern for direct delegation, rather than a finished specification every agent already implements, keeps expectations honest.

A2A vs MCP: the sideways edge, not the downward one

The sharpest way to place A2A is by the edge of the system it governs, because A2A and MCP are routinely framed as rivals when they sit on different axes. MCP, the Model Context Protocol, standardizes the downward edge: how an agent reaches the tools, data, and context it consumes — a database, a file store, a ticketing system, a shared piece of mission context — through one interface. A2A standardizes the sideways edge: how one agent asks another agent to take on work and return a result. One connects an agent to capabilities; the other connects an agent to peers. They are not two answers to one question.

Because they govern different edges, they compose rather than substitute. An agent can speak MCP to pull the context and tools it needs, then speak A2A to delegate a sub-task to a specialist agent that, in turn, uses its own MCP connections to do the work. Draw the system as a graph and the split is mechanical: MCP edges run agent-to-server, A2A edges run agent-to-agent. Asking whether to use A2A or MCP is a category error, like asking whether to use HTTP or a message queue — they solve adjacent problems, and a mature estate will want both.

The confusion has a real source: both are open protocols pitched at multi-agent systems, and both promise cross-vendor interoperability. But what each makes reusable differs. MCP makes a tool reusable by any agent that speaks it. A2A makes an agent reusable as a callable participant by any other agent that speaks it. Keeping the two boundaries distinct is what lets a platform team adopt them on independent timelines: you can put MCP behind tool and context access today, before the agent-to-agent layer has converged, and reach for A2A where direct delegation patterns prove out.

The new problem A2A introduces: governing delegation across vendors

The interesting thing about A2A is not that it lets agents call each other — bespoke glue already does that. It is that the moment delegation becomes a standard channel rather than a hand-built one, delegation chains get longer and cross more vendor lines, and that is precisely where the governance problem appears. When agent A delegates to agent B, which delegates to agent C, the work, the cost, and the accountability for it travel down a path no single agent has a full view of. A protocol that frames the request and the result does not, by itself, tell a platform owner who delegated what to whom, what each hop consumed, or whether the final result matched the original intent.

This is why an open and inspectable agent-to-agent channel matters more than a proprietary one, beyond connectivity. If delegation happens inside one vendor's private wiring, the platform team that is accountable for the estate cannot see across the chain — they get a result and a bill, with the path that produced them opaque. An open A2A standard is attractive for the same structural reason MCP is, but the payoff here is specifically observability of delegation: the difference between trusting each vendor's account of what its agents did and being able to reconstruct it yourself.

None of that observability comes from the delegation protocol on its own, though, which is the part most A2A enthusiasm skips. Knowing who owns a piece of work right now, catching the moment two delegated agents conflict on the same context, and producing an auditable record of the whole chain are concerns that live a layer above any agent-to-agent wire format. A2A makes the handoffs reusable; it does not make them governable. Something has to sit over the chain to do that, which is the same gap MCP leaves on its own edge.

The pragmatic stance: coordinate through MCP today, treat A2A as a roadmap path

For a platform team deciding how to coordinate agents now, the honest recommendation is to build on MCP today and treat A2A as a forward path. MCP is the protocol the largest set of agents already speak, it is conceptually stable and openly specified, and it is enough to let many agents share one piece of work: expose coordination context as an MCP server, and any MCP-speaking agent can join, read the current state, and write back its contribution through one interface. That gives cross-vendor coordination that functions today, without betting the architecture on an agent-to-agent layer that has not yet settled.

Coordinating through a shared, MCP-exposed context also covers more of the multi-agent problem than direct delegation alone. The hard parts of running many agents on the same work are not just passing a task from one agent to the next — they are keeping a shared source of truth, knowing which agent currently owns a piece of work, catching the moment two agents act on the same context and conflict, and producing an auditable record of who did what. Those concerns sit above any single protocol, so a control plane can provide them today over MCP while the agent-to-agent layer matures underneath.

Treating A2A as a roadmap path, rather than ignoring it or overcommitting to it, is the position that ages well. The direct-delegation patterns A2A standardizes are genuinely useful and worth adopting as they stabilize, so the right move is to design the coordination layer to speak agent-to-agent protocols when they are ready — layering them onto the same shared context, ownership, and conflict model coordination already runs on — without rebuilding around them prematurely. Building on the open integration point that exists now and adding the next one as it matures is how an estate keeps working across vendors through the transition.

Where Quordo fits

Quordo is a cross-vendor control plane with two surfaces on one plane: SPEND for AI cost governance and COORDINATE for multi-agent coordination. COORDINATE speaks MCP today, which is what makes the argument above more than theory: any MCP agent such as Claude Code, Devin, or Cursor can join a mission, read and write shared versioned context, and report its runs through one standard interface. Around that connection Quordo adds the coordination layer no single protocol provides on its own — explicit handoffs so it is always clear which agent owns a piece of work, an append-only auditable trace spanning fifteen event types, optimistic-concurrency conflict detection, and coherence, the share of a mission's context with no open conflicts, as the headline alignment metric. Per-run agent cost reconciles into per-mission spend, so a multi-agent mission stays both aligned and accountable on the same plane as cost governance.

A2A is on Quordo's roadmap, not in the product today, and we would rather say that plainly than overclaim. The architecture is built so agent-to-agent delegation can be added as those patterns stabilize, layered onto the same shared context, trace, and conflict model coordination already runs on — which is exactly the over-the-chain governance the protocol leaves open. Until then, coordinating through MCP gives you working cross-vendor multi-agent coordination now, with the agent-to-agent path treated as the next step rather than a promise the present product cannot keep.

Frequently asked questions

What is A2A (agent-to-agent)?: A2A is an emerging approach for autonomous agents to interact as peers: advertise capabilities, delegate tasks to each other with the context needed to complete them, and exchange results and status — without every connection being hand-built. It targets the N-times-M integration problem at the agent-to-agent edge specifically.
What is the difference between A2A and MCP?: They govern different edges of the system. MCP standardizes how an agent reaches the tools, data, and context it consumes — edges run agent-to-server. A2A standardizes how one agent asks another agent to take on work — edges run agent-to-agent. They compose rather than substitute, and a mature estate will want both.
Should I build on A2A now or wait?: Coordinate through MCP today — it is the protocol most agents already speak and it is enough to let many agents share one piece of work through a shared context server. Treat A2A as a forward path: adopt its direct-delegation patterns as they stabilize, layered onto the same shared context, ownership, and conflict model you already run.