Read a paid endpoint's 402 challenge without paying it

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x38287535a4f47f53360940cfad8bf9ac5bc04a69",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "20000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "body": {
          "expected_amount_usd": "0.01",
          "expected_network": "eip155:8453",
          "url": "https://api.example/paid"
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "example": {
          "accepts": [
            {
              "amount_usd": 0.01,
              "network": "eip155:8453",
              "pay_to": "0x…"
            }
          ],
          "failures": [],
          "protocol": "x402-v2",
          "receipt": {
            "algorithm": "ed25519",
            "key_id": "…",
            "receipt_id": "01J…",
            "signature": "…"
          },
          "status_code": 402,
          "url": "https://api.example/paid",
          "verdict": "payable"
        },
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "body": {
              "properties": {
                "expected_amount_usd": {
                  "description": "Optional. Price in USD the challenge should carry.",
                  "type": "string"
                },
                "expected_network": {
                  "description": "Optional. CAIP-2 network such as eip155:8453.",
                  "type": "string"
                },
                "expected_pay_to": {
                  "description": "Optional. Address the challenge should pay to.",
                  "type": "string"
                },
                "url": {
                  "description": "The paid http(s) route to probe.",
                  "type": "string"
                }
              },
              "required": [
                "url"
              ]
            },
            "bodyType": {
              "enum": [
                "json",
                "form-data",
                "text"
              ],
              "type": "string"
            },
            "method": {
              "enum": [
                "POST"
              ],
              "type": "string"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method",
            "bodyType",
            "body"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  }
}

curl "https://sentinel.rootstuff.io/x402/payment-envelope"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://sentinel.rootstuff.io/x402/payment-envelope");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://sentinel.rootstuff.io/x402/payment-envelope")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header