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Aegis is a stateless x402 API. No signup, no API keys. You need:
  1. A wallet on Base with a small USDC balance.
  2. A signing client that can produce an X-PAYMENT header. The Coinbase x402 SDK ships clients for Python, TypeScript/JavaScript, Go, and Java.
Both Base mainnet and Base Sepolia (testnet) are supported. Start on Sepolia for free testing before flipping to real USDC.

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1. Discover the price list

No payment, no auth. 
curl https://x402.aegis-kyt.com/.well-known/x402.json | jq

{
  "name": "Aegis KYT x402 API",
  "services": [
    { "endpoint": "/screen/{chain}/{address}",           "price": "0.10", "asset": "USDC", "network": "base", "available": true  },
    { "endpoint": "/check-address/{chain}/{address}",      "price": "1.00", "asset": "USDC", "network": "base", "available": true  },
    { "endpoint": "/check-transfer/{chain}/{tx_hash}",   "price": "0.50", "asset": "USDC", "network": "base", "available": true  }
  ]
}

​
2. Probe the quote

Hit any tier path without payment — the server replies 402 with a machine-readable quote. 
curl -i https://x402.aegis-kyt.com/screen/eth/0x6b175474e89094c44da98b954eedeac495271d0f

HTTP/2 402
payment-required: <base64-encoded JSON quote>

{}
Decode the payment-required header to get: 
{
  "x402Version": 2,
  "accepts": [{
    "scheme":  "exact",
    "network": "eip155:84532",
    "asset":   "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
    "amount":  "100000",
    "payTo":   "0x6d0A788caC92d83FB827CDfb07C0D111e97Acfb6",
    "maxTimeoutSeconds": 300,
    "extra":   { "name": "USDC", "version": "2" }
  }]
}
amount is in USDC base units (6 decimals — 100000 = $0.10).

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3. Sign and retry

Use the Coinbase x402 client to sign the quote against your wallet and retry with the X-PAYMENT header. 
from x402.client import x402Client
from eth_account import Account
import httpx

# Your wallet (Base Sepolia for testing, real key for mainnet)
account = Account.from_key("0x" + "your-test-key-here")

client = x402Client(account=account)

# httpx client — the x402 client wraps it transparently
async with httpx.AsyncClient() as http:
    response = await client.get(
        http,
        "https://x402.aegis-kyt.com/screen/eth/0x6b175474e89094c44da98b954eedeac495271d0f",
    )
    print(response.json())

​
4. Receive the answer

{
  "schema_version": 1,
  "address": "0x6b175474e89094c44da98b954eedeac495271d0f",
  "chain": "ETH",
  "labels": [
    {
      "source":      "provider_a-verdicts",
      "source_name": "provider_a",
      "label":       "DAI Stablecoin Contract",
      "category":    "stablecoin",
      "confidence":  92,
      "source_url":  "https://...",
      "first_seen_at": "2025-08-12T00:00:00Z",
      "last_seen_at":  "2026-04-29T00:00:00Z"
    }
  ],
  "risk": {
    "risk_level":          "none",
    "risk_score":          0,
    "is_risky":            false,
    "risk_categories":     [],
    "source_count":        9,
    "confidence":          94,
    "primary_source_slug": "provider_a-verdicts",
    "label":               "DAI Stablecoin",
    "consensus_found":     true
  }
}
Replay protection is on by default — the same X-PAYMENT header won’t authorize a second call. Sign a fresh one for each request.

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Next steps

  • Authentication deep-dive — exactly what’s in the X-PAYMENT header.
  • Endpoint reference — per-tier request/response.
  • Networks — supported {chain} values.
  • Risk categories — taxonomy returned in risk.risk_categories[] from the screening tiers.
  • Running pre-send screens at high volume? Switch to V2 API’s POST /v2/screen — same data, settled via subscription quota instead of per-call USDC.