Check a URL before fetching it: is it alive, final URL after redirects, HTTP status, conte

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x06b40bf8Dfdc45049ea7f600c84301E227a2Ca15",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "5000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "method": "GET",
        "queryParams": {
          "ua": "my-agent/1.0",
          "url": "https://example.com/"
        },
        "type": "http"
      },
      "output": {
        "example": {
          "alive": true,
          "contentType": "text/html; charset=UTF-8",
          "finalUrl": "https://example.com/",
          "redirects": [],
          "requestedUrl": "https://example.com/",
          "robots": {
            "allowed": true,
            "fetched": true,
            "group": "*",
            "matchedRule": null
          },
          "status": 200,
          "timingMs": 350,
          "title": "Example Domain"
        },
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "method": {
              "enum": [
                "GET"
              ],
              "type": "string"
            },
            "queryParams": {
              "properties": {
                "ua": {
                  "description": "User-agent to evaluate robots.txt against",
                  "type": "string"
                },
                "url": {
                  "description": "Absolute http(s) URL to check",
                  "type": "string"
                }
              },
              "required": [
                "url"
              ],
              "type": "object"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  }
}

curl "https://toolbelt402.tpoborne.workers.dev/url/preflight"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://toolbelt402.tpoborne.workers.dev/url/preflight");
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://toolbelt402.tpoborne.workers.dev/url/preflight")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header