The Mannequin Context Protocol (MCP) and Agent-to-Agent (A2A) have gained a big business consideration over the previous 12 months. MCP first grabbed the world’s consideration in dramatic style when it was printed by Anthropic in November 2024, garnering tens of 1000’s of stars on GitHub throughout the first month. Organizations shortly noticed the worth of MCP as a strategy to summary APIs into pure language, permitting LLMs to simply interpret and use them as instruments. In April 2025, Google launched A2A, offering a brand new protocol that enables brokers to find one another’s capabilities, enabling the fast progress and scaling of agentic methods.
Each protocols are aligned with the Linux Basis and are designed for agentic methods, however their adoption curves have differed considerably. MCP has seen fast adoption, whereas A2A’s progress has been extra of a sluggish burn. This has led to business commentary suggesting that A2A is quietly fading into the background, with many individuals believing that MCP has emerged because the de-facto normal for agentic methods.
How do these two protocols examine? Is there actually an epic battle underway between MCP and A2A? Is that this going to be Blu-ray vs. HD-DVD, or VHS vs. Betamax yet again? Properly, not precisely. The fact is that whereas there’s some overlap, they function at completely different ranges of the agentic stack and are each extremely related.
MCP is designed as a manner for LLMs to grasp what exterior instruments can be found to it. Earlier than MCP, these instruments have been uncovered primarily via APIs. Nonetheless, uncooked API dealing with by an LLM is clumsy and troublesome to scale. LLMs are designed to function on this planet of pure language, the place they interpret a process and establish the fitting instrument able to undertaking it. APIs additionally undergo from points associated to standardization and versioning. For instance, if an API undergoes a model replace, how would the LLM find out about it and use it accurately, particularly when attempting to scale throughout 1000’s of APIs? This shortly turns into a show-stopper. These have been exactly the issues that MCP was designed to resolve.
Architecturally, MCP works effectively—that’s, till a sure level. Because the variety of instruments on an MCP server grows, the instrument descriptions and manifest despatched to the LLM can change into huge, shortly consuming the immediate’s complete context window. This impacts even the most important LLMs, together with these supporting tons of of 1000’s of tokens. At scale, this turns into a elementary constraint. Lately, there have been spectacular strides in decreasing the token depend utilized by MCP servers, however even then, the scalability limits of MCP are prone to stay.
That is the place A2A is available in. A2A doesn’t function on the stage of instruments or instrument descriptions, and it doesn’t become involved within the particulars of API abstraction. As an alternative, A2A introduces the idea of Agent Playing cards, that are high-level descriptors that seize the general capabilities of an agent, quite than explicitly itemizing the instruments or detailed expertise the agent can entry. Moreover, A2A works solely between brokers, that means it doesn’t have the power to work together straight with instruments or finish methods the way in which MCP does.
So, which one must you use? Which one is best? In the end, the reply is each.
In case you are constructing a easy agentic system with a single supervisory agent and a wide range of instruments it could entry, MCP alone will be a super match—so long as the immediate stays compact sufficient to suit throughout the LLM’s context window (which incorporates your complete immediate finances, together with instrument schemas, system directions, dialog state, retrieved paperwork, and extra). Nonetheless, if you’re deploying a multi-agent system, you’ll very doubtless want so as to add A2A into the combination.
Think about a supervisory agent answerable for dealing with a request comparable to, “analyze Wi-Fi roaming issues and suggest mitigation methods.” Reasonably than exposing each potential instrument straight, the supervisor makes use of A2A to find specialised brokers—comparable to an RF evaluation agent, a person authentication agent, and a community efficiency agent—primarily based on their high-level Agent Playing cards. As soon as the suitable agent is chosen, that agent can then use MCP to find and invoke the particular instruments it wants. On this circulate, A2A gives scalable agent-level routing, whereas MCP gives exact, tool-level execution.
The important thing level is that A2A can—and sometimes ought to—be utilized in live performance with MCP. This isn’t an MCP versus A2A choice; it’s an architectural one, the place each protocols will be leveraged because the system grows and evolves.
The psychological mannequin I like to make use of comes from the world of networking. Within the early days of pc networking, networks have been small and self-contained, the place a single Layer-2 area (the information hyperlink layer) was adequate. As networks grew and have become interconnected, the boundaries of Layer-2 have been shortly reached, necessitating the introduction of routers and routing protocols—often known as Layer-3 (the community layer). Routers perform as boundaries for Layer-2 networks, permitting them to be interconnected whereas additionally stopping broadcast site visitors from flooding your complete system. On the router, networks are described in higher-level, summarized phrases, quite than exposing all of the underlying element. For a pc to speak exterior of its rapid Layer-2 community, it should first uncover the closest router, understanding that its meant vacation spot exists someplace past that boundary.
This maps carefully to the connection between MCP and A2A. MCP is analogous to a Layer-2 community: it gives detailed visibility and direct entry, however it doesn’t scale indefinitely. A2A is analogous to the Layer-3 routing boundary, which aggregates higher-level details about capabilities and gives a gateway to the remainder of the agentic community.
The comparability will not be an ideal match, however it provides an intuitive psychological mannequin that resonates with those that have a networking background. Simply as trendy networks are constructed on each Layer-2 and Layer-3, agentic AI methods will finally require the complete stack as effectively. On this mild, MCP and A2A shouldn’t be considered competing requirements. In time, they are going to doubtless each change into essential layers of the bigger agentic stack as we construct more and more refined AI methods.
The groups that acknowledge this early would be the ones that efficiently scale their agentic methods into sturdy, production-grade architectures.
