The x402 version 2 402 response

When a resource costs money, an x402 seller answers with HTTP 402 and puts its quote in the PAYMENT-REQUIRED response header. The value is base64 of a UTF-8 JSON object. The response body is free-form and clients should not depend on it.

Headers in the exchange

Header	Sent by	Carries
`PAYMENT-REQUIRED`	Seller, on the 402	The quote: what to pay, to whom, on which network
`PAYMENT-SIGNATURE`	Buyer, on the retry	The option it accepted and its signed payment
`PAYMENT-RESPONSE`	Seller, on the final response	The settlement result, including the transaction hash

Version 1 used an X-PAYMENT request header and put the quote in the response body. The endpoint checker reports which version an endpoint speaks.

A decoded quote

This is what https://x402testendpoint.com/t/ok sends, after base64 decoding:

{
  "x402Version": 2,
  "resource": {
    "url": "https://x402testendpoint.com/t/ok",
    "description": "What is being sold",
    "mimeType": "application/json"
  },
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:84532",
      "asset": "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
      "amount": "1000",
      "payTo": "0xSellerWalletAddress",
      "maxTimeoutSeconds": 60,
      "extra": {
        "name": "USDC",
        "version": "2"
      }
    }
  ]
}

Fields

Field	Meaning
`x402Version`	`2` for this format.
`error`	Optional. Why the previous payment attempt was rejected. See the error reference.
`resource.url`	The URL being paid for. Buyers can compare it with what they requested.
`resource.description`	Optional but useful: tells agents and catalogs what is being sold.
`accepts`	One or more ways to pay. The buyer picks one it supports.
`accepts[].scheme`	How the payment works. `exact` means a fixed amount.
`accepts[].network`	A CAIP-2 identifier, such as `eip155:8453` for Base or `eip155:84532` for Base Sepolia.
`accepts[].asset`	The token contract address.
`accepts[].amount`	The price in the token's smallest unit, as a string. USDC has six decimals, so `1000` is 0.001 USDC.
`accepts[].payTo`	The seller's receiving address.
`accepts[].maxTimeoutSeconds`	How long the buyer's signed payment should stay valid.
`accepts[].extra`	Scheme-specific data. For `exact` on EVM, the token's EIP-712 `name` and `version`, which the buyer needs in order to sign.
`extensions`	Optional add-ons, such as the Bazaar extension that lets facilitator catalogs index the endpoint.

Check or decode one

Paste a header into the header decoder to see what it contains.
Run the endpoint checker on a URL to validate its quote field by field.
Fetch a known-good example with curl -i https://x402testendpoint.com/t/ok.

Field names and the header encoding follow the types and helpers in @x402/core 2.31.