Official daily foreign exchange reference rates from the European Central Bank (~30 curren

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x9862ca83b72aB95521F457aFf6e6EFb03d8164C3",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "5000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "method": "GET",
        "queryParams": {
          "base": "USD",
          "symbols": "EUR,GBP,JPY,CHF"
        },
        "type": "http"
      },
      "output": {
        "example": {
          "base": "USD",
          "date": "2026-08-17",
          "notice": "ECB euro foreign exchange reference rates, available free of charge at ecb.europa.eu; non-EUR bases are cross-rates computed via EUR.",
          "rates": {
            "CHF": 0.809885,
            "EUR": 0.862589,
            "GBP": 0.737514,
            "JPY": 159.225395
          },
          "source": "ECB"
        },
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "additionalProperties": false,
          "properties": {
            "method": {
              "enum": [
                "GET"
              ],
              "type": "string"
            },
            "queryParams": {
              "additionalProperties": false,
              "properties": {
                "base": {
                  "default": "EUR",
                  "description": "Base currency as ISO 4217 code (case-insensitive). EUR or any of the ~30 ECB-listed currencies (USD, GBP, JPY, CHF, ...); non-EUR bases are computed as cross-rates via EUR. Default: EUR.",
                  "examples": [
                    "EUR",
                    "USD",
                    "GBP"
                  ],
                  "pattern": "^[A-Za-z]{3}$",
                  "type": "string"
                },
                "symbols": {
                  "description": "Optional comma-separated ISO 4217 codes to restrict the rate table to (case-insensitive); codes the ECB does not list are ignored. Empty = all listed currencies.",
                  "examples": [
                    "USD,GBP,JPY",
                    "CHF"
                  ],
                  "type": "string"
                }
              },
              "required": [],
              "type": "object"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "properties": {
                "base": {
                  "description": "Base currency of the rate table (ISO 4217)",
                  "type": "string"
                },
                "date": {
                  "description": "ECB reference date of the rates (YYYY-MM-DD, last business day)",
                  "type": "string"
                },
                "notice": {
                  "description": "ECB attribution notice: the underlying data is available free of charge from the ECB; cross-rates are computed values",
                  "type": "string"
                },
                "rates": {
                  "additionalProperties": {
                    "type": "number"
                  },
                  "description": "Units of each quoted currency per 1 unit of base, e.g. rates.USD = USD per base. ECB publishes vs EUR; other bases are cross-rates via EUR rounded to 6 decimals.",
                  "type": "object"
                },
                "source": {
                  "description": "Always \"ECB\" — European Central Bank euro foreign exchange reference rates",
                  "type": "string"
                }
              },
              "required": [
                "base",
                "date",
                "rates",
                "source",
                "notice"
              ],
              "type": "object"
            },
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  }
}

curl "https://4yearcycle.com/x402/fx-rates"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://4yearcycle.com/x402/fx-rates");
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://4yearcycle.com/x402/fx-rates")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header