Current Base mainnet block height and base fee per gas in wei, read from the chain at requ

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xa0f3c29f25778dDf46fce2cAB5f7e7C25E6a1451",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "method": "GET",
        "queryParams": {},
        "type": "http"
      },
      "output": {
        "example": {
          "baseFeePerGas": "1043211",
          "blockHeight": "35812044",
          "network": "eip155:8453",
          "observedAt": "2026-09-15T14:00:00.000Z"
        },
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "method": {
              "enum": [
                "GET"
              ],
              "type": "string"
            },
            "queryParams": {
              "properties": {},
              "type": "object"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "properties": {
                "baseFeePerGas": {
                  "description": "Base fee per gas of that block, in wei, decimal string",
                  "type": "string"
                },
                "blockHeight": {
                  "description": "Latest block number on Base mainnet, decimal string",
                  "type": "string"
                },
                "network": {
                  "description": "CAIP-2 chain id, always eip155:8453",
                  "type": "string"
                },
                "observedAt": {
                  "description": "ISO 8601 time the chain was read",
                  "type": "string"
                }
              },
              "required": [
                "blockHeight",
                "baseFeePerGas",
                "network",
                "observedAt"
              ],
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  }
}

curl "https://canary.countersignpay.com/v1/base/head"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://canary.countersignpay.com/v1/base/head");
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://canary.countersignpay.com/v1/base/head")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header