Verify Payment (EOA)

Verify an EIP-712 signed payment payload before settlement

Validates an EIP-712 TransferWithAuthorization signature against on-chain state. Call this before /settle to confirm the payment is executable.

POST /verify

Request Body

Field	Type	Description
paymentPayload	object	Signed payment data
paymentPayload.token	string	Token contract address
paymentPayload.payload	object	Authorization and signature
paymentPayload.payload.authorization	object	EIP-712 authorization fields
paymentPayload.payload.authorization.from	string	Payer wallet address
paymentPayload.payload.authorization.to	string	Recipient wallet address
paymentPayload.payload.authorization.value	string	Amount in wei (uint256)
paymentPayload.payload.authorization.validAfter	number	Unix timestamp, signature valid after
paymentPayload.payload.authorization.validBefore	number	Unix timestamp, signature valid before
paymentPayload.payload.authorization.nonce	string	Random bytes32 nonce
paymentPayload.payload.signature	string	EIP-712 signature
paymentRequirements	object	Network and contract details
paymentRequirements.network	string	Target network ("bsc" or "base")
paymentRequirements.relayerContract	string	b402 Relayer contract address

Response

Valid Payment (200)

Field	Type	Description
isValid	boolean	true if the payment can be settled
payer	string	Recovered signer address

Invalid Payment (200)

Field	Type	Description
isValid	boolean	false
invalidReason	string	Why the payment failed verification

Verification Checks

The facilitator runs these checks in order:

1. Signature recovery - Recovers the signer from the EIP-712 signature and confirms it matches authorization.from
2. Nonce uniqueness - Checks the nonce has not been used or canceled on-chain
3. Time window - Confirms validAfter <= now <= validBefore
4. Token whitelisting - Verifies the token is whitelisted on the Relayer contract
5. Balance and allowance - Checks the payer has sufficient token balance and has approved the Relayer contract

A valid verification does not guarantee settlement will succeed. On-chain state can change between verify and settle calls. Always settle promptly after verification.

Examples

cURL

curl -X POST https://facilitatorv3.b402.ai/verify \
  -H "Content-Type: application/json" \
  -d '{
    "paymentPayload": {
      "token": "0x55d398326f99059fF775485246999027B3197955",
      "payload": {
        "authorization": {
          "from": "0xAbC1234567890aBcDeF1234567890AbCdEf123456",
          "to": "0x9876543210FeDcBa9876543210FeDcBa98765432",
          "value": "10000000000000000",
          "validAfter": 1709251200,
          "validBefore": 1709254800,
          "nonce": "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
        },
        "signature": "0xabc123...eip712_signature"
      }
    },
    "paymentRequirements": {
      "network": "bsc",
      "relayerContract": "0xE91b564EB8DFF305Ff8efA332f84c487b9da5171"
    }
  }'

TypeScript

const response = await fetch("https://facilitatorv3.b402.ai/verify", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    paymentPayload: {
      token: "0x55d398326f99059fF775485246999027B3197955",
      payload: {
        authorization: {
          from: wallet.address,
          to: recipientAddress,
          value: "10000000000000000",
          validAfter: Math.floor(Date.now() / 1000),
          validBefore: Math.floor(Date.now() / 1000) + 3600,
          nonce: crypto.randomBytes(32).toString("hex"),
        },
        signature: eip712Signature,
      },
    },
    paymentRequirements: {
      network: "bsc", // or "base"
      relayerContract: "0xE91b564EB8DFF305Ff8efA332f84c487b9da5171",
    },
  }),
});

const result = await response.json();

if (result.isValid) {
  console.log("Payment verified. Payer:", result.payer);
  // Proceed to /settle
} else {
  console.error("Verification failed:", result.invalidReason);
}

Error Codes

Code	HTTP Status	Description
signature_error	400	EIP-712 signature is malformed or recovery failed
nonce_error	400	Nonce has already been used or was canceled
payment_verification_error	400	Balance insufficient, allowance too low, or token not whitelisted
validation_error	400	Request body is missing required fields or has invalid types

Related

• Settle Payment (EOA) - Execute settlement after verification
• EIP-712 Signature Guide - Construct signatures for this endpoint
• Quickstart - Get started with b402