A2A vs. Other Protocols

Before we explore A2A’s core components and real examples, it helps to see where it fits in the broader protocol landscape. Different protocols solve problems, and the most capable systems combine them rather than relying on a single approach.

A2A is often mentioned alongside MCP (Model Context Protocol). They sound similar but address different layers. Broadly, today’s protocols fall into two categories:

• Context-oriented protocols govern how agents interact with external tools, APIs, and data. MCP belongs here. It lets a model or agent gain new capabilities by connecting to functions, services, and knowledge sources.

• Inter-agent protocols govern how agents communicate with one another, exchange structured information, negotiate roles, and collaborate. A2A belongs here. It provides a shared language so multiple agents can coordinate work securely and predictably.

Now, let’s examine each in more detail to see that they aren’t either/or options, but are designed to work together.

How does A2A differ from MCP?

MCP standardizes tool access. Think of it as a workshop: the agent learns tool names, parameters, and outputs. It excels at well-defined, deterministic tasks such as fetching rows from a database, calling a weather API, or running a summarization function, so you do not have to custom-wire every API.

A2A focuses on something different: how independent agents communicate and coordinate. If MCP is the workshop, A2A is the coordination room. It gives multiple agents a shared language to discover one another, agree on responsibilities, exchange context, stream progress, and deliver results securely, without needing to peek into each other’s internals. It is designed for delegation, collaboration, and orchestrating complex workflows across specialized agents.

These are complementary, not competing. MCP gives each agent dependable tool access, and A2A gives those agents a dependable way to collaborate. Most real-world systems use MCP within agents and A2A between agents.

How does A2A differ from other inter-agent protocols?

Many groups are developing inter-agent standards, including ACP, Agora, and Agent Protocol. Approaches vary: some target web-based, cross-vendor interoperability, while others focus on local, edge, or domain-specific setups. ACP (IBM/BeeAI) and A2A are the most prominent efforts.

A2A takes a web-based path for cross-platform, cross-vendor collaboration. It uses familiar building blocks such as HTTP, JSON-RPC, and SSE, so it integrates smoothly into enterprise stacks and supports distributed, multi-team workflows across frameworks and clouds.

ACP evolved for local or edge autonomy in low-latency, network-lean settings such as IoT, robotics, or privacy-sensitive deployments. It supports multiple transports (REST, gRPC, ZeroMQ, and local buses), favors offline discovery and cloud-independent operation, and modifies resource use. This makes it strong where bandwidth is limited, but less focused on out-of-the-box cross-vendor interoperability.

The good news is that we won’t have to make an informed choice anymore regarding which one to pick. This is because ACP has now merged into A2A under the Linux Foundation, with IBM contributing to A2A’s direction and migration paths available for ACP and BeeAI users. The takeaway is simple: momentum converges on one open, vendor-neutral collaboration layer (A2A) that pairs naturally with MCP for tool access.

What’s next?

Now that we’ve placed A2A in context and compared it with other major protocols, it’s time to get hands-on. In the upcoming lessons, we’ll explore the core components of the A2A protocol, the building blocks that make secure, structured agent collaboration possible.

We’ll explain how discovery, capabilities, requests, streaming, and errors work together to create reliable agent-to-agent interactions. Finally, we’ll examine the famous “Agent Card” mentioned throughout the lessons; this compact JSON document tells other agents exactly what you can do and how to communicate with you.