How do I install the X402 Client skill?

Run npx skillmds@latest add modbender/x402-client-2 in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is X402 Client safe to use?

This skill has not completed SkillMD's automated safety review yet. Independent scanners report: SkillSpector: PASS, Skill Scanner: PASS. Capability flags: executes scripts, makes network calls. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with X402 Client?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is X402 Client free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published X402 Client?

modbender (@modbender) published this skill. Their other Agent Skills are listed on their SkillMD profile.

X402 Client by modbender — Agent Skill

Name: X402 Client
Rating: 4.666666666666667 (3 reviews)
Author: modbender

X402 Client

Make paid API requests using the x402 HTTP payment protocol (USDC on Base Sepolia). Use when you need to access x402-protected services, pay for API calls with crypto, or perform web searches via an x402 search gateway. Handles wallet setup, payment signing, and request retry automatically.

modbender Updated Sep 22, 2026 12 repo stars

File contents

x402 Client

Make HTTP requests to x402-protected APIs. The x402 protocol uses HTTP 402 responses to request payment — this skill handles signing USDC payments and retrying automatically.

Prerequisites

Node.js 18+ installed
A Base Sepolia wallet with ETH (gas) and USDC (payments)

First-Time Setup

1. Install dependencies

bash <skill-dir>/scripts/setup.sh

This installs the x402 SDK to ~/.x402-client/. Only needed once.

2. Generate a wallet (if you don't have one)

node <skill-dir>/scripts/wallet-gen.mjs --out ~/.x402-client/wallet.key

3. Fund the wallet

Get testnet tokens from faucets:

Base Sepolia ETH (gas): https://www.alchemy.com/faucets/base-sepolia
Base Sepolia USDC (payments): https://faucet.circle.com/ → select Base Sepolia + USDC

Send both to the wallet address printed by wallet-gen.

4. Store the key

Set the environment variable for future use:

export X402_PRIVATE_KEY=$(cat ~/.x402-client/wallet.key)

Or pass --key-file ~/.x402-client/wallet.key to each request.

Making Paid Requests

Use x402-fetch.mjs to make any x402-paid HTTP request:

# Search the web ($0.001 USDC per query)
node <skill-dir>/scripts/x402-fetch.mjs \
  "https://<service-url>/web/search?q=latest+AI+news&count=5" \
  --key-file ~/.x402-client/wallet.key

The script automatically:

Makes the HTTP request
If 402 received, parses payment requirements
Signs a USDC payment with your wallet
Retries with the payment header
Outputs the response JSON to stdout

All scripts must be run from ~/.x402-client/ (where node_modules lives):

cd ~/.x402-client && node <skill-dir>/scripts/x402-fetch.mjs "<url>" --key-file wallet.key

Known Services

See references/services.md for a list of known x402 endpoints including a web search service.

Troubleshooting

"insufficient funds": Wallet needs more USDC or ETH. Use faucets above.
402 with no auto-payment: Ensure setup.sh was run and you're executing from ~/.x402-client/.
Tunnel URL not working: The service URL may have changed. Ask the service operator or check /health.

---name: x402-client-2description: Make paid API requests using the x402 HTTP payment protocol (USDC on Base Sepolia). Use when you need to access x402-protected services, pay for API calls with crypto, or perform web searches via an x402 search gateway. Handles wallet setup, payment signing, and request retry automatically.---# x402 ClientMake HTTP requests to x402-protected APIs. The x402 protocol uses HTTP 402 responses to request payment — this skill handles signing USDC payments and retrying automatically.## Prerequisites- Node.js 18+ installed- A Base Sepolia wallet with ETH (gas) and USDC (payments)## First-Time Setup### 1. Install dependencies```bashbash <skill-dir>/scripts/setup.sh```This installs the x402 SDK to `~/.x402-client/`. Only needed once.### 2. Generate a wallet (if you don't have one)```bashnode <skill-dir>/scripts/wallet-gen.mjs --out ~/.x402-client/wallet.key```### 3. Fund the walletGet testnet tokens from faucets:- **Base Sepolia ETH** (gas): https://www.alchemy.com/faucets/base-sepolia- **Base Sepolia USDC** (payments): https://faucet.circle.com/ → select Base Sepolia + USDCSend both to the wallet address printed by wallet-gen.### 4. Store the keySet the environment variable for future use:```bashexport X402_PRIVATE_KEY=$(cat ~/.x402-client/wallet.key)```Or pass `--key-file ~/.x402-client/wallet.key` to each request.## Making Paid RequestsUse `x402-fetch.mjs` to make any x402-paid HTTP request:```bash# Search the web ($0.001 USDC per query)node <skill-dir>/scripts/x402-fetch.mjs \ "https://<service-url>/web/search?q=latest+AI+news&count=5" \ --key-file ~/.x402-client/wallet.key```The script automatically:1. Makes the HTTP request2. If 402 received, parses payment requirements3. Signs a USDC payment with your wallet4. Retries with the payment header5. Outputs the response JSON to stdoutAll scripts must be run from `~/.x402-client/` (where node_modules lives):```bashcd ~/.x402-client && node <skill-dir>/scripts/x402-fetch.mjs "<url>" --key-file wallet.key```## Known ServicesSee [references/services.md](references/services.md) for a list of known x402 endpoints including a web search service.## Troubleshooting- **"insufficient funds"**: Wallet needs more USDC or ETH. Use faucets above.- **402 with no auto-payment**: Ensure setup.sh was run and you're executing from `~/.x402-client/`.- **Tunnel URL not working**: The service URL may have changed. Ask the service operator or check `/health`.

Frequently asked questions