Metrics Roll Spread

{
  "components": {
    "absoluteCovariance": 2.583251,
    "covariance": 2.583251,
    "interpretation": "absolute_covariance_proxy",
    "intervals": 30,
    "mode": "absolute",
    "observations": 28,
    "strictRollDefined": false
  },
  "computedAt": "2026-05-23T14:00:00.000Z",
  "coverage": {
    "completeFetch": true,
    "coverageRatio": 1,
    "effectiveWindowMinutes": 30,
    "errorMessage": null,
    "partialData": false,
    "requestedWindowMinutes": 30
  },
  "exchange": "coinbase",
  "firstTradeTime": "2026-05-23T13:00:02.000Z",
  "lastTradeTime": "2026-05-23T13:59:58.000Z",
  "metric": "roll-spread",
  "pair": "BTC-USD",
  "tradeCount": 428,
  "value": 3.2145,
  "window": "30m"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://api.dripmetrics.ai/metrics/roll-spread?exchange=coinbase&pair=BTC-USD&window=30m'

# 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://api.dripmetrics.ai/metrics/roll-spread?exchange=coinbase&pair=BTC-USD&window=30m' \
  | 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 $0.05 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.05" });
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 $0.05 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fapi.dripmetrics.ai%2Fmetrics%2Froll-spread
const res = await pay("https://api.dripmetrics.ai/metrics/roll-spread?exchange=coinbase&pair=BTC-USD&window=30m");
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 $0.05 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.05"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://api.dripmetrics.ai/metrics/roll-spread?exchange=coinbase&pair=BTC-USD&window=30m")
    print(res.status_code, res.text)