Exchanges Spread

{
  "arbitrage_note": "best bid exceeds best ask by 0.0332% before fees and transfer time; gaps this small are usually below typical taker fees (0.1-0.6%), so not a realistic arbitrage",
  "base": "ETH",
  "best_ask": {
    "exchange": "gemini",
    "price": 2474.53
  },
  "best_bid": {
    "exchange": "bitfinex",
    "price": 2475.3523
  },
  "cross_exchange_gap_pct": 0.0332,
  "exchanges": [
    {
      "ask": 2476.4509,
      "bid": 2475.3523,
      "exchange": "bitfinex",
      "last": 2476.5508,
      "premium_vs_median_pct": 0.063,
      "quote": "USDT",
      "volume_24h_base": 20914.87195166,
      "volume_24h_usd": 51796743
    },
    {
      "ask": 2474.62,
      "bid": 2474.61,
      "exchange": "bitstamp",
      "last": 2474.42,
      "premium_vs_median_pct": -0.023,
      "quote": "USD",
      "volume_24h_base": 15575.502967,
      "volume_24h_usd": 38540336
    },
    {
      "ask": 2474.78,
      "bid": 2474.69,
      "exchange": "coinbase",
      "last": 2474.92,
      "premium_vs_median_pct": -0.002,
      "quote": "USD",
      "volume_24h_base": 79829.48634149,
      "volume_24h_usd": 197571592
    },
    {
      "ask": 2474.6033,
      "bid": 2474.5933,
      "exchange": "gateio",
      "last": 2474.6033,
      "premium_vs_median_pct": -0.015,
      "quote": "USDT",
      "volume_24h_base": 159068.7258,
      "volume_24h_usd": 393631994
    },
    {
      "ask": 2474.53,
      "bid": 2474.52,
      "exchange": "gemini",
      "last": 2475.3,
      "premium_vs_median_pct": 0.013,
      "quote": "USD",
      "volume_24h_base": 1039.732447,
      "volume_24h_usd": 2573650
    },
    {
      "ask": 2475.01,
      "bid": 2475,
      "exchange": "kraken",
      "last": 2475,
      "premium_vs_median_pct": 0.001,
      "quote": "USD",
      "volume_24h_base": 24062.23573284,
      "volume_24h_usd": 59554033
    },
    {
      "ask": 2474.9628,
      "bid": 2474.9528,
      "exchange": "kucoin",
      "last": 2474.9628,
      "premium_vs_median_pct": -0.001,
      "quote": "USDT",
      "volume_24h_base": 30677.18678304,
      "volume_24h_usd": 75924896
    },
    {
      "ask": 2475.1526,
      "bid": 2475.1426,
      "exchange": "mexc",
      "last": 2475.8716,
      "premium_vs_median_pct": 0.036,
      "quote": "USDT",
      "volume_24h_base": 87969.32961,
      "volume_24h_usd": 217800765
    }
  ],
  "exchanges_checked": 8,
  "exchanges_responding": 8,
  "high_low_last_spread_pct": 0.0861,
  "median_last": 2474.9814,
  "quote_note": "prices in USD; USDT-settled books (bitfinex, gateio, kucoin, mexc) are converted with the live Kraken USDT/USD rate",
  "usdt_usd_rate": 0.99873
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://saylorinnovations.com/api/crypto/exchanges/spread?base=ETH'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://saylorinnovations.com/api/crypto/exchanges/spread?base=ETH' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

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

// Pays at most $0.01 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.01" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.01 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fsaylorinnovations.com%2Fapi%2Fcrypto%2Fexchanges%2Fspread
const res = await pay("https://saylorinnovations.com/api/crypto/exchanges/spread?base=ETH");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.01 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.01"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://saylorinnovations.com/api/crypto/exchanges/spread?base=ETH")
    print(res.status_code, res.text)