Quick Start (5 Minutes)

Get up and running with 4SEC API. No signup, no API keys, just your wallet.

Prerequisites

• Python 3.9+ or Node.js 18+
• Crypto wallet with USDC on Base network

Step 1: Install x402 Client

# Python
pip install x402-client httpx eth-account

# JavaScript
npm install @x402/client ethers

Step 2: Setup Wallet

from eth_account import Account
from x402.client import X402Client

wallet = Account.from_key("0x_your_private_key_here")
client = X402Client(wallet=wallet, facilitator_url="https://x402.org/facilitator")

Step 3: First Request

response = client.get("https://api.foursec.xyz/price/ETH")
data = response.json()

print(f"Symbol: {data['symbol']}")
print(f"Price: ${data['price_usd']}")
print(f"24h Change: {data['change_24h']}%")
print(f"Sources: {data['total_sources']} DEXes")

Expected Response

{
  "symbol": "ETH",
  "price_usd": 2450.32,
  "change_24h": 2.45,
  "volume_24h_usd": 12500000,
  "total_sources": 3,
  "spread": 0.07,
  "sources": [
    {"dex": "Uniswap V3", "price": 2450.30, "liquidity_usd": 5200000},
    {"dex": "BaseSwap", "price": 2450.35, "liquidity_usd": 3100000},
    {"dex": "SushiSwap", "price": 2450.28, "liquidity_usd": 4200000}
  ]
}

Step 4: Try More Endpoints

# Arbitrage opportunities ($0.03)
arb = client.get("https://api.foursec.xyz/arbitrage-opportunity").json()

# Historical data ($0.02)
history = client.get("https://api.foursec.xyz/price/history/ETH?interval=1h&limit=24").json()

# Risk metrics ($0.02)
risk = client.get("https://api.foursec.xyz/volatility-index/ETH").json()

What Just Happened?

1. You sent GET request to the API
2. API returned 402 Payment Required
3. x402 client automatically signed USDC transfer
4. Client retried with payment proof
5. API verified and returned data
6. Total cost: $0.01 USDC

INFO

Same request within 30s is free (served from cache).

Next Steps

• API Reference — All endpoints
• Python SDK — Advanced usage
• How x402 Works — Payment protocol deep dive