---
title: "MCP, A2A and x402: What Each One Does When You Look for AI Tools"
summary: "Ask an assistant for a product comparison that includes the latest release details, and it first has to read release notes and official documentation, then turn that material into conclusions with sources. Searching, reading repositories and fetching data all depend on specific tools and services."
author: "AgentTools"
tags: ["MCP", "A2A", "x402"]
canonical_url: null
url: "https://agent-tools.cloud/articles/mcp-a2a-x402-explained"
content_hash: "1d5241026d5b16755338fa9386e9ba7a187733c5e9d704aa814a40610cf5b64b"
---

Ask an assistant for a product comparison that includes the latest release details, and it first has to read release notes and official documentation, then turn that material into conclusions with sources. Searching, reading repositories and fetching data all depend on specific tools and services.

When you look for those tools, MCP, A2A and x402 often appear in the same directory. They solve different problems: MCP connects tools and data, A2A connects independent agents, and x402 handles payment when a resource costs money.

| Name | What it mainly solves | An example |
|---|---|---|
| MCP | How an AI application connects to tools and data | Reading a code repository, querying issues |
| A2A | How independent agents communicate and work together | Handing a research task to a research agent |
| x402 | How a client pays for an HTTP resource programmatically | Using a paid data API per request |

## MCP: Connecting Tools to an Assistant

MCP stands for Model Context Protocol. A provider exposes tools and their input requirements through MCP. An AI application that supports the matching connection type can discover those tools, call them and use what comes back.

GitHub's official MCP server is a concrete example. It can read repositories and code files, manage issues and pull requests, and inspect workflows. Once it is connected, an assistant can read a project's documentation, look up related issues and answer from the material it retrieved.

Those capabilities still come from the GitHub platform and its API. MCP standardizes how the assistant talks to the tool. Which tools are available and which repositories can be reached depend on the server configuration and the permissions granted, and the client has to support the local or remote connection the server uses.

The protocol is versioned by dated revisions, and a client and server agree on one during the handshake. When our directory probed MCP servers on November 11, 2026 and offered the current revision, 2026-07-28, 3,997 of the reachable servers accepted it, while 18,500 settled on 2025-11-25. An older revision is not a fault in itself, but it tells you which protocol features to expect.

## A2A: Handing a Task to Another Agent

A report can also be produced by several independent agents. The main assistant might give a research agent the scope and the expected deliverable, and the research agent decides how to work and returns the result.

A2A, short for Agent2Agent, is the protocol these independent agents use to communicate. The two sides can be built on different frameworks and still cooperate around tasks and results, without merging their internals into one system. The research skill belongs to the agent; A2A lets the two sides understand each other.

An agent describes itself in an Agent Card: its skills, its endpoints and the protocol versions it supports. Version 1.0 lists these under `supportedInterfaces`, so one agent can serve 1.0 and the older 0.3 side by side. Among reachable agents in our directory on November 11, 2026, 1,771 declared 1.0 as their highest version and 2,258 still topped out at 0.3.

While reading a repository, the research agent can still use MCP. MCP tools can wrap complex operations too, so the useful distinction is whether you are connecting to a tool or to an independent agent, not how many steps the job takes.

## x402: Putting Payment Into the Request

Some data APIs charge per request. A client that supports x402 can handle the payment requirement as part of the HTTP exchange, so paid access can be completed by a program.

The typical flow: the client requests a resource, the server answers `402 Payment Required` with its payment requirements, the client prepares and submits a payment payload, and the server verifies and settles it under the chosen scheme before delivering the resource.

x402 is a payment standard that an ordinary HTTP API can adopt; the API does not need to support MCP or A2A. The network, asset and amount are set by each service. The client still needs a way to pay, and the application still controls authorization and budget. x402 handles paid access; it does not plan the research for the agent. On November 11, 2026, 7,644 x402 listings in our directory were reachable and had answered our probes with a valid 402 challenge.

## Start From the Task in Front of You

The three can be combined. One report workflow: the assistant reads project material through MCP, delegates focused research through A2A, and, when paid data is needed, an x402-capable client fetches it within an agreed authorization and budget. Each step depends on whether the chosen services and clients support it; the protocol names do not wire anything up by themselves.

If the report only needs public documentation, one tool that retrieves the right material may be enough. When choosing a service, look first at what material it covers and what it returns, then check whether it connects to the assistant you use. Add agent collaboration or paid access when there is a clear reason for it.

## What a Directory Listing Can Tell You

Tags in a tool directory narrow the candidates. A listing can also show whether the service answered recent probes, which protocol version it speaks and whether its description is complete. On agent-tools.cloud each listing carries a quality grade, which sets search order, and a separate readiness score that checks how fully the listing follows its protocol.

Neither replaces a test on your own task. Whether a service fits is decided by the work: can it retrieve the material you need, keep the sources, and support the conclusions you have to draw?

## References

- [GitHub's Official MCP Server](https://github.com/github/github-mcp-server)
- [MCP Specification, Revision 2026-07-28](https://modelcontextprotocol.io/specification/2026-07-28)
- [A2A Protocol: Overview and Relationship to MCP](https://a2a-protocol.org/latest/)
- [A2A Protocol Specification](https://a2a-protocol.org/latest/specification/)
- [x402 Documentation](https://docs.x402.org/)
- [Agent Tools: How Grading and Readiness Work](https://agent-tools.cloud/about#readiness)