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Agent skill

X402 Express Wrapper

by majiayu000 in majiayu000/claude-skill-registry

Wrapper oficial de M2MCent (Node.js) para inyectar muros de pago x402 en APIs o servidores Model Context Protocol (MCP).

MITAuto-check: notesAgent Workflows

Install X402 Express Wrapper

skills CLI
$ npx skills add majiayu000/claude-skill-registry --skill x402-express-wrapper -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install majiayu000/claude-skill-registry x402-express-wrapper --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/majiayu000/claude-skill-registry.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/api/x402-express-wrapper .claude/skills/x402-express-wrapper && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
x402-express-wrapper
GitHub stars
666
Used in
2 other repos
Token cost
~765 tokens
SKILL.md length
259 words
Files
2
Skills in repo
1,273
Repo updated
First seen
Licence
MIT

At a glance

Wrapper oficial de M2MCent (Node.js) para inyectar muros de pago x402 en APIs o servidores Model Context Protocol (MCP).

  • Works in 3 steps: "Agregar una barrera de pago a la API". → "Monetizar el servidor MCP que acabamos… → "Exigir micropagos en USDC por usar el…
  • Tasks that involve MCP servers
  • SKILL.md covers When to Use, 📦 Instalación, 🛠️ Implementación and 🧠 Consideraciones…, plus 1 more section
  • Calls npm; reaches mainnet.base.org; needs RELAYER_PRIVATE_KEY

What it does

X402 Express Wrapper is an agent skill from majiayu000/claude-skill-registry. Wrapper oficial de M2MCent (Node.js) para inyectar muros de pago x402 en APIs o servidores Model Context Protocol (MCP). Usar al construir nuevos servicios que requieran monetización máquina a máquina.

Its SKILL.md is about 770 tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file (for example `metadata.json`).

It sits in Agent Workflows, covering MCP servers. It works with x402, Model Context Protocol and Node.js. The repository describes itself as: Searchable Claude Code skills catalog with source-linked guides and generated registry artifacts. The licence is MIT.

When your agent uses it

  • Tasks that involve MCP servers

Example prompts

  • “/x402-express-wrapper”

Requirements

  • Node.js
  • A credential in RELAYER_PRIVATE_KEY

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

  1. "Agregar una barrera de pago a la API".
  2. "Monetizar el servidor MCP que acabamos de crear".
  3. "Exigir micropagos en USDC por usar el endpoint".

What it can do on your machine

Read from SKILL.md and the folder at commit 2d14a69. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • npm

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Hosts in commands or code, which the agent is likely to contact:

    • mainnet.base.org

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names these keys or tokens, usually read from environment variables:

    • RELAYER_PRIVATE_KEY

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

X402 Express Wrapper loads about 765 tokens when it runs. Until then it costs about 56 tokens; SKILL.md has 259 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~56
When it runs · the whole SKILL.md, loaded when a task matches
~765

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

  • NoteMentions a .env fileSKILL.md:56
    erificar que sus variables de entorno de .env coincidan con el wrapper.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from majiayu000/claude-skill-registry at commit 2d14a69, republished under its MIT licence (© majiayu000). 259 words, ~765 tokens.

Download SKILL.mdSave it as .claude/skills/x402-express-wrapper/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
x402-express-wrapper
description
Wrapper oficial de M2MCent (Node.js) para inyectar muros de pago x402 en APIs o servidores Model Context Protocol (MCP). Usar al construir nuevos servicios que requieran monetización máquina a máquina.
risk
critical
source
community
tags
x402, defi, monetization, express, mcp

x402-express-wrapper

Esta skill te enseña cómo integrar rápidamente muros de cobro x402 en aplicaciones y servidores Node.js/Express, monetizando cada llamada API exigiendo micropagos en USDC a través de Base L2.

When to Use

Usa esta skill cuando el usuario humano (u otro Agente) te solicite:

  1. "Agregar una barrera de pago a la API".
  2. "Monetizar el servidor MCP que acabamos de crear".
  3. "Exigir micropagos en USDC por usar el endpoint".

📦 Instalación

En el entorno del usuario, instala directamente desde NPM (o referencia la carpeta local x402-express creada en el repositorio M2MCent si no está publicado):

bash
npm install x402-express ethers

🛠️ Implementación

Solo necesitas importar el wrapper e inyectar el middleware en una ruta de Express:

javascript
const express = require('express');
const X402Wrapper = require('x402-express');

const app = express();

// 🚨 PROTOCOL LOCKING: El escrowAddress está harcodeado en la v1.1+. 
// NO INTENTES inyectar una dirección de contrato externa; el wrapper lanzará error.
const x402 = new X402Wrapper({
    rpcUrl: "https://mainnet.base.org",
    privateKey: process.env.RELAYER_PRIVATE_KEY, // OBLIGATORIO
    recipient: process.env.MY_WALLET_ADDRESS     // OBLIGATORIO: Tu beneficio neto
});

// Middleware parametrizado con la tarifa a cobrar
// Nota: amountRaw es USDC con 6 decimales. "20000" = $0.02
app.get('/api/premium', x402.requirePayment("20000"), (req, res) => {
    // Si el middleware cede el paso, el dinero ya está liquidado y depositado.
    res.json({ data: "Información Valiosa", receipt: req.paymentTx });
});

🧠 Consideraciones Arquitectónicas (Agentic Context)

  1. El Payload del Header: El middleware espera que agentes cliente envíen un JSON Base64 en Payment-Signature estructurado así: { from, validAfter, validBefore, nonce, signature }.
  2. Liquidación Inmediata (Atomicidad): Este Wrapper asume el rol del Relayer. Por tanto, el propio servidor web se encarga de llamar a M2MCentEscrow.settle() on-chain. ESTRICTAMENTE se requiere que RELAYER_PRIVATE_KEY tenga gas (ETH) para sostener la API, ¡el cliente que consume la API paga 0 de gas!

Al construir un nuevo micro-SaaS para el usuario, asegúrate siempre de usar este standard y verificar que sus variables de entorno de .env coincidan con el wrapper.

Limitations

  • Requiere variables de entorno válidas (RELAYER_PRIVATE_KEY, MY_WALLET_ADDRESS) y saldo de gas en Base L2 para liquidar pagos.
  • Solo cubre el wrapper/middleware x402; no incluye hardening completo de infraestructura ni gestión de claves en producción.
  • Está orientado a Node.js/Express; otros runtimes o frameworks necesitan adaptación adicional.

© majiayu000, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file in skills/api/x402-express-wrapper of majiayu000/claude-skill-registry.

  • SKILL.md
  • metadata.json

Open the folder on GitHubat commit 2d14a69

Used in 2 other repositories

We found 6 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 2 other GitHub owners. This page covers the copy in majiayu000/claude-skill-registry, which our catalogue first saw on October 8, 2026.

Compare with similar skills

X402 Express Wrapper next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

X402 Express Wrapper compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
X402 Express Wrapper this skillmajiayu000/claude-skill-registry6662 repos~765Automated safety check: NotesMIT
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Vinkius Deployvinkius-labs/mcpfusion256—~1.7kAutomated safety check: NotesApache-2.0
Meting AgentELDment/Meting-Agent112—~583Automated safety check: PassMIT
Meridian MCPMeridiona/meridian411—~967Automated safety check: NotesCustom licence
Claude HistorianVvkmnn/claude-historian-mcp179—~616Automated safety check: PassMIT

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Works with

Categories

Questions about X402 Express Wrapper

What does X402 Express Wrapper do?

Wrapper oficial de M2MCent (Node.js) para inyectar muros de pago x402 en APIs o servidores Model Context Protocol (MCP). X402 Express Wrapper is an agent skill from majiayu000/claude-skill-registry.js) para inyectar muros de pago x402 en APIs o servidores Model Context Protocol (MCP).

When should I use X402 Express Wrapper?

X402 Express Wrapper fits situations like: tasks that involve MCP servers.

How do I install X402 Express Wrapper in Claude Code?

Run `npx skills add majiayu000/claude-skill-registry --skill x402-express-wrapper -a claude-code`. Or copy the skill folder (skills/api/x402-express-wrapper in majiayu000/claude-skill-registry) into .claude/skills/x402-express-wrapper in your project. Claude Code loads it when a task matches its description.

How do I install X402 Express Wrapper in Codex?

Run `npx skills add majiayu000/claude-skill-registry --skill x402-express-wrapper -a codex`. Or copy the skill folder (skills/api/x402-express-wrapper in majiayu000/claude-skill-registry) into .agents/skills/x402-express-wrapper in your project. Codex loads it when a task matches its description.

Can I use X402 Express Wrapper in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add majiayu000/claude-skill-registry --skill x402-express-wrapper -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/x402-express-wrapper, .gemini/skills/x402-express-wrapper, .github/skills/x402-express-wrapper and .opencode/skills/x402-express-wrapper in your project.

What does X402 Express Wrapper need to run?

Going by SKILL.md and its folder, X402 Express Wrapper needs the command-line tools its instructions call (npm) and credentials named RELAYER_PRIVATE_KEY. Our summary lists: Node.js; A credential in RELAYER_PRIVATE_KEY.

Does X402 Express Wrapper access the network?

SKILL.md names 1 domain. In commands or code: mainnet.base.org; the agent is likely to contact it when it follows the instructions. This is read from the text; nothing was executed.

Is X402 Express Wrapper safe to install?

Our automated static check of SKILL.md found notes only (mentions a .env file), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.

What licence does X402 Express Wrapper use?

X402 Express Wrapper is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does X402 Express Wrapper use?

About 765 tokens (SKILL.md is roughly 3.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to X402 Express Wrapper?

Skills that share tags, products or a category with X402 Express Wrapper: agentmemory Setup and Diagnostics (rohitg00/agentmemory, 29k stars), Vinkius Deploy (vinkius-labs/mcpfusion, 256 stars), Meting Agent (ELDment/Meting-Agent, 112 stars) and Meridian MCP (Meridiona/meridian, 411 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains X402 Express Wrapper?

majiayu000 (a GitHub user) maintains it in majiayu000/claude-skill-registry, which has 666 GitHub stars. The repository holds 1,273 skills in this directory. The repository was last updated on October 7, 2026.

Source: majiayu000/claude-skill-registry on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.