Who it is for

Agents that get paid, pay or monitor wallets.

• Confirm a payment arrived
• Check balance before buying

How an agent buys it

POST https://a-upgradenet.com/x402/base-balance
Content-Type: application/json

{
  "address": "0x4200000000000000000000000000000000000006",
  "tokens": [
    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
  ]
}

1) Answers 402 with the price (PAYMENT-REQUIRED)
2) The agent signs the payment (EIP-3009, USDC on Base) and repeats with PAYMENT-SIGNATURE
3) Receives the result + PAYMENT-RESPONSE

Example response

{
  "status": "completed",
  "chain": "base",
  "address": "0x…",
  "block_number": "21000000",
  "eth": "0.0123",
  "eth_wei": "12300000000000000",
  "tokens": [
    {
      "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "symbol": "USDC",
      "decimals": 6,
      "balance": "25.5",
      "raw": "25500000"
    }
  ]
}