Quickstart for Sellers

Accept and settle x402 payments through Paratro’s Facilitator

Quickstart for Sellers

This guide shows how to verify and settle x402 payment authorizations using Paratro as your Facilitator.

Prerequisites

• A Paratro API key and secret
• A receiving account on a supported chain

Accept a Payment

1. Receive payment from buyer

   The buyer sends a signed x402 payment payload (ERC-3009, Permit2, or Solana format).

2. Verify the signature

   Call POST /x402/verify to validate the payment authorization:

   curl -X POST https://api.paratro.com/api/v1/x402/verify \
     -H "Authorization: Bearer $TOKEN" \
     -H "Content-Type: application/json" \
     -d '{
       "x402Version": 2,
       "paymentPayload": {
         "payload": {
           "signature": "0x...",
           "authorization": {
             "from": "0xPayerAddress",
             "to": "0xYourAddress",
             "value": "1000000",
             "validAfter": "0",
             "validBefore": "1774601102",
             "nonce": "0x..."
           }
         },
         "accepted": {
           "scheme": "exact",
           "network": "eip155:84532",
           "asset": "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
           "amount": "1000000",
           "payTo": "0xYourAddress"
         }
       }
     }'
   

   Response:

   {
     "isValid": true,
     "payer": "0xPayerAddress"
   }
   
3. Settle on-chain

   Call POST /x402/settle with the same payload to execute the transfer:

   curl -X POST https://api.paratro.com/api/v1/x402/settle \
     -H "Authorization: Bearer $TOKEN" \
     -H "Content-Type: application/json" \
     -d '{ ... same payload as verify ... }'
   

   Response:

   {
     "success": true,
     "transaction": "0xabc123...",
     "payer": "0xPayerAddress",
     "network": "eip155:84532"
   }
   
4. Check settlement status

   curl https://api.paratro.com/api/v1/x402/settle/TX_ID \
     -H "Authorization: Bearer $TOKEN"
   

Settling with upto Scheme

For variable-amount payments, include extra.settlementAmount in the payment requirements:

{
  "x402Version": 2,
  "paymentPayload": {
    "payload": { "signature": "0x...", "permit2Authorization": { ... } },
    "accepted": {
      "scheme": "upto",
      "network": "eip155:84532",
      "asset": "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
      "amount": "5000000",
      "payTo": "0xYourAddress",
      "extra": {
        "assetTransferMethod": "permit2",
        "settlementAmount": "300000"
      }
    }
  }
}

Field	Description
amount	Maximum authorized by the buyer (5 USDC)
extra.settlementAmount	Actual amount to settle (0.30 USDC)

settlementAmount must be less than or equal to amount. If set to "0", no on-chain transaction is executed.