x402 Conformance

Name: x402 Conformance
Author: atsp-protocol

by atsp-protocolversion 1.6.0i★ –iRuns on your computer

Registry nameio.github.atsp-protocol/x402-conformance

Install

Overview

Description from the maker (original English)

x402 payment safety checks: validate a 402 answer, prove a server never serves before settlement.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Online shops & payments

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
The registry lists no key to fill in.

You need

npmNode.js installed (for the npx command)

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "x402-conformance": {
      "command": "npx",
      "args": [
        "-y",
        "x402-conformance-mcp"
      ]
    }
  }
}

Run this in your terminal

claude mcp add x402-conformance -- npx -y x402-conformance-mcp

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "x402-conformance": {
      "command": "npx",
      "args": [
        "-y",
        "x402-conformance-mcp"
      ]
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "x402-conformance": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "x402-conformance-mcp"
      ]
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account atsp-protocol, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Online shops & paymentsi

More stars than 0% of the other 1749 servers in this category
Published to the registry more recently than 70% of the other 1749 servers in this category
Basic checks equal to or better than 100% of the other 1749 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is x402 Conformance safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (1.6.0) reached the registry 13 days ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Node.js, Docker on your computer.

What can I use instead?

In the same category: Spree Commerce: open-source B2B and marketplace ecommerce, Stripe MCP, MCP Cn Commerce

Alternatives

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Install

Stripe MCP

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Stripe’s official server lets AI view and manage customers, products, payments and invoices. Connect to Stripe’s cloud and sign in with OAuth.

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Install

MCP Cn Commerce

by TonyWang-hub

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Runs on your computer★ 96MITUpdated 28 days ago

Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

x402-conformance-mcp

x402 conformance and safety checks as tools, for MCP clients (Claude, Cursor, VS Code, Windsurf and others), the Vercel AI SDK and LangChain. It's a thin entry point into the open x402-conformance suite: the same checks and check IDs as the CLI, the GitHub Action and the test matchers, and the full x402-conformance.report/1 report. It never pays, signs or touches mainnet.

MCP

{ "mcpServers": { "x402-conformance": { "command": "npx", "args": ["-y", "x402-conformance-mcp"] } } }

The same server runs from the Docker image, which starts it on stdio when given no arguments: { "mcpServers": { "x402-conformance": { "command": "docker", "args": ["run", "-i", "--rm", "ghcr.io/atsp-protocol/x402-conformance:1"] } } }. npx -y x402-conformance-mcp --version prints the version, and --help prints the client config and a link to docs/USING.md.

tool	arguments	what it does
`x402_check_payment_required`	`url`, http or https	one unpaid GET to a paid URL; checks its 402 answer (P1-P7)
`x402_demo`	`fault`, optional: `none` or `serve_on_any_settle`	P1-P7 and R0-R10 against a built-in demo server, no wallet or setup; `fault: serve_on_any_settle` shows a failure
`x402_start_facilitator_double`	`port`, optional; 0 or omitted picks a free one	starts the facilitator double on loopback; point your server at its URL
`x402_probe_resource_server`	`resource_url` on loopback; `network`, optional: `auto`, `solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1` or `eip155:84532`	R0-R10 against your server on loopback: no content on a timeout, a broken answer, `settlement_pending`, a failure or a duplicate. Start the double first
`x402_stop_facilitator_double`	none	stops the double
`x402_explain_check`	`id`, for example `R3`, `P5` or `R11a`	what a check tests and how to fix a failure, from docs/FIXES.md
`x402_share_case`	`report` from another x402 tool; optional `framework`, `sdk`, `sdk_version`, `network`	an anonymised corpus case and a pre-filled issue link; nothing is sent, the user decides

Try asking: "Run the x402 demo", "Check the 402 answer at http://127.0.0.1:4020/paid", or "Start the facilitator double, I'll point my server at it, then probe http://127.0.0.1:4020/paid".

Vercel AI SDK

import { generateText } from "ai";

import { x402ConformanceTools } from "x402-conformance-mcp/ai-sdk";

await generateText({ model, tools: x402ConformanceTools(), prompt: "Is the 402 answer at https://api.example.com/paid valid x402?" });

LangChain and LangGraph

import { createReactAgent } from "@langchain/langgraph/prebuilt";

import { x402ConformanceTools } from "x402-conformance-mcp/langchain";

const agent = createReactAgent({ llm, tools: x402ConformanceTools() });

The AI SDK and LangChain adapters give an agent the four read-only tools (check, demo, explain, share). The double and probe tools stay in MCP, where a person is driving. The adapters need ai 5.0.0 or later, or @langchain/core 0.3.0 or later, installed next to them; both are optional peer dependencies.

The corpus

A failing report can become an anonymised case in the public corpus of real x402 failures. x402_share_case prepares it and returns the link; the user reviews it and submits it, or doesn't. Every report names the entry point that produced it (via: mcp, ai-sdk or langchain) in the report and the User-Agent; there's no other identifier and no telemetry.

Apache-2.0. Ryan Gillespie / Optitransfer.

x402 Conformance

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Online shops & paymentsi

Common questions

Alternatives

Spree Commerce: open-source B2B and marketplace ecommerce

Stripe MCP

MCP Cn Commerce

README from the maker

x402-conformance-mcp

MCP

Vercel AI SDK

LangChain and LangGraph

The corpus