Live gas cost comparison across Base, OP Mainnet, Arbitrum One, and Ethereum in one call,

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x0D083590c048A243e24a75E3a7C968145DE25B44",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "method": "GET",
        "queryParams": {
          "gasLimit": 21000
        },
        "type": "http"
      },
      "output": {
        "example": {
          "baseRank": 1,
          "baseVsEthereum": "Base is 240.5x cheaper than Ethereum",
          "basis": "current gas price x gasLimit",
          "chains": [
            {
              "baseFeePerGas": "0.005",
              "blockNumber": "49106604",
              "chain": "base",
              "chainId": 8453,
              "estimatedCost": {
                "eth": "0.000000126",
                "gasLimit": 21000,
                "gwei": "126"
              },
              "gasPrice": "0.006",
              "label": "Base"
            }
          ],
          "cheapest": "base",
          "fetchedAt": "2026-07-25T18:02:36.639Z",
          "gasLimit": 21000,
          "unavailable": []
        },
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "method": {
              "enum": [
                "GET"
              ],
              "type": "string"
            },
            "queryParams": {
              "properties": {
                "gasLimit": {
                  "default": 21000,
                  "description": "Gas units to price each chain against. Defaults to 21000 (a plain ETH transfer).",
                  "maximum": 30000000,
                  "minimum": 21000,
                  "type": "integer"
                }
              },
              "required": [],
              "type": "object"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  },
  "builder-code": {
    "info": {
      "a": "bc_lhfd8zad"
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "additionalProperties": false,
      "properties": {
        "a": {
          "description": "App builder code",
          "pattern": "^[a-z0-9_]{1,32}$",
          "type": "string"
        },
        "s": {
          "description": "Service builder codes",
          "items": {
            "pattern": "^[a-z0-9_]{1,32}$",
            "type": "string"
          },
          "type": "array"
        },
        "w": {
          "description": "Wallet builder code",
          "pattern": "^[a-z0-9_]{1,32}$",
          "type": "string"
        }
      },
      "type": "object"
    }
  }
}

curl "https://base-gas-x402-production.up.railway.app/gas/compare"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://base-gas-x402-production.up.railway.app/gas/compare");
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://base-gas-x402-production.up.railway.app/gas/compare")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header