Buyer-side payment firewall: should THIS agent make THIS payment now? Where /api/assess ve

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x1A9Fa76f5b420e85DE147C4419638BEbE64D6dE5",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "2000",
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "payTo": "4uLqY8BnJuA7CFxRork2FnNMu2u9NsJquF8Cc6V5B5jB",
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "amount": "2000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "body": {},
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "body": {
              "properties": {
                "agent_id": {
                  "description": "The calling agent's wallet (keys per-agent history). Optional — auto-filled from the x402 payer if omitted.",
                  "type": "string"
                },
                "context": {
                  "description": "Where the payment instruction came from (provenance).",
                  "properties": {
                    "expected_payto": {
                      "description": "The payTo the agent intended, to detect routing swaps.",
                      "type": "string"
                    },
                    "metadata": {
                      "type": "object"
                    },
                    "source": {
                      "description": "e.g. \"tool_output\", \"web_content\".",
                      "type": "string"
                    }
                  },
                  "type": "object"
                },
                "payment": {
                  "description": "The payment instruction being vetted.",
                  "properties": {
                    "amount": {
                      "type": "number"
                    },
                    "asset": {
                      "description": "e.g. \"USDC\"",
                      "type": "string"
                    },
                    "payto_address": {
                      "description": "Address the payment would go to — 0x EVM (Base) OR base58 Solana.",
                      "type": "string"
                    },
                    "resource_url": {
                      "description": "The resource being paid for.",
                      "type": "string"
                    }
                  },
                  "required": [
                    "payto_address"
                  ],
                  "type": "object"
                },
                "policy": {
                  "description": "Optional checks, e.g. {check_counterparty: true}.",
                  "type": "object"
                }
              }
            },
            "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"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  }
}

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

const res = await fetch("https://402sentinel.com/api/firewall");
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://402sentinel.com/api/firewall")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header