BTC exchange rates

BTC-denominated exchange rates for ~60 units: crypto (ETH, LTC, BNB, SOL, ...), fiat (USD, EUR, JPY, ...) and commodities (gold, silver ounces), each as units per 1 BTC with name and type. Send GET /api/exchange-rates with no required fields (2 optional) and pay $0.005 per call over x402 or MPP (there is no free tier). It returns a JSON object with source, fetchedAt, cached, base, count and 1 more.

Optional `currencies` filter (comma-separated unit codes) and `type` filter (crypto, fiat, commodity). One call gives a consistent cross-rate table: BTC in gold ounces, ETH/BTC, USD/JPY via BTC. Cached in-process for 60 seconds.

Category: Crypto & onchain data · Tags: crypto exchange-rates btc fiat gold cross-rate fx

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Parameters

Example request

curl -i "https://agent402.tools/api/exchange-rates?currencies=usd%2Ceur%2Ceth%2Cxau"

Without payment this returns HTTP 402 Payment Required with the exact price for exchange-rates; any x402 v2 or MPP client pays it and retries.

Example response

{
  "source": "coingecko",
  "fetchedAt": "2026-08-22T13:20:00.000Z",
  "cached": false,
  "base": "BTC",
  "count": 4,
  "rates": [
    {
      "code": "usd",
      "name": "US Dollar",
      "unit": "$",
      "type": "fiat",
      "perBtc": 77018
    },
    {
      "code": "eur",
      "name": "Euro",
      "unit": "€",
      "type": "fiat",
      "perBtc": 65600.2
    },
    {
      "code": "eth",
      "name": "Ether",
      "unit": "ETH",
      "type": "crypto",
      "perBtc": 31.813
    },
    {
      "code": "xau",
      "name": "Gold - Troy Ounce",
      "unit": "XAU",
      "type": "commodity",
      "perBtc": 22.91
    }
  ]
}

From an MCP client

catalog.call {
  "slug": "exchange-rates",
  "params": {
    "currencies": "usd,eur,eth,xau"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for exchange-rates; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• Every field is optional. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key (Authorization: Bearer a402_...) also pays it.
• A POST with a JSON body to /api/exchange-rates is served as this GET, with the body as the input.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/exchange-rates?currencies=usd%2Ceur%2Ceth%2Cxau");

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