Pay-per-call Setup

Base URL

All examples use the dedicated x402 host:

https://x402-data-tools.prd.arrays.org

Do not point x402 clients at data-tools.prd.arrays.org. That host is API-key auth and answers a bare GET with 401, so the SDK never sees the 402 challenge. (It does return 402 if you add Accept-Payment: x402, but stock SDKs don’t send that header.)

Prerequisites

An EVM wallet
Funds on one of the supported rails: USDC deposited via Circle Gateway (settles on Base), or USDC / USDT / USD1 in your wallet on BNB Chain
x402-fetch (Node) or x402-requests (Python) installed — any x402 v2 client works

Step 0 — See the 402 challenge (no wallet needed)

curl -i "https://x402-data-tools.prd.arrays.org/api/v1/crypto/funding-rate?symbol=BTCUSDT"

HTTP/2 402
payment-required: eyJhY2NlcHRzIjpb...        (base64 x402 v2 payload)

{
  "success": false,
  "error": { "code": "PAYMENT_REQUIRED", "message": "x402 payment required for this endpoint" },
  "request_id": "...",
  "x402Version": 2,
  "accepts": [
    { "scheme": "exact", "network": "eip155:8453", "amount": "8000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0x9548E84DA0713a5c06b5D2CBB48d9670f1e27632", "maxTimeoutSeconds": 345600,
      "extra": { "name": "GatewayWalletBatched", "version": "1",
                 "verifyingContract": "0x77777777Dcc4d5A8B6E418Fd04D8997ef11000eE" } },
    { "scheme": "exact", "network": "eip155:56", "amount": "8000000000000000",
      "asset": "0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d",
      "extra": { "name": "USD Coin", "assetTransferMethod": "permit2-exact", "..." : "..." } }
  ],
  "resource": { "url": "/api/v1/crypto/funding-rate", "mimeType": "application/json" }
}

Pick one accepts entry, sign it, and retry with the PAYMENT-SIGNATURE header. The SDKs below do this for you.

TypeScript example

npm install x402-fetch viem

import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";
import { wrapFetchWithPayment } from "x402-fetch";

const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`);
const client = createWalletClient({ account, chain: base, transport: http() });

// Wrap fetch with x402 payment support
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

// Make a paid call — no API key needed
const res = await fetchWithPayment(
  "https://x402-data-tools.prd.arrays.org/api/v1/crypto/funding-rate?symbol=BTCUSDT"
);

console.log(await res.json());

That’s it. The first call returns 402; wrapFetchWithPayment automatically signs, retries, and returns the data. The settlement result (tx, network, payer) is in the PAYMENT-RESPONSE header of the 200.

Python example

pip install x402-requests

import os
from x402_requests import X402Session
from eth_account import Account

account = Account.from_key(os.environ["PRIVATE_KEY"])
session = X402Session(account=account, chain="base")

res = session.get(
    "https://x402-data-tools.prd.arrays.org/api/v1/crypto/funding-rate",
    params={"symbol": "BTCUSDT"},
)
print(res.json())

Cost math

How much will it actually cost?

Use case	Calls / month	Tier	Cost
Daily funding-rate snapshot	30	$0.008	$0.24
Hourly funding-rate for 10 pairs	7,200	$0.008	$57.60
Crypto screener every 5 min	8,640	$0.03	$259.20

At sustained high volume, a subscription plan usually becomes cheaper than per-call nanopayment. Mix both: subscription for steady workloads, Nanopayment for spikes.

Troubleshooting

Errors come back as 402 with the standard envelope; the facilitator’s message is forwarded in error.message.

401 UNAUTHORIZED — API key is required

You are calling data-tools.prd.arrays.org. Switch to x402-data-tools.prd.arrays.org, or add Accept-Payment: x402.

404 X402_NOT_SUPPORTED

The route is not one of the 15 priced endpoints. See the list.

402 INSUFFICIENT_BALANCE

Base rail: deposit USDC into Circle Gateway. BNB Chain rail: fund the signing wallet with the chosen asset.

402 PAYMENT_ALREADY_USED

Nonce reuse. Generate a fresh 32-byte nonce for every call.

402 PAYMENT_VALIDITY_TOO_SHORT

validBefore - validAfter must be at least maxTimeoutSeconds from the 402 (345600s on Base).

402 PAYMENT_INVALID_SIGNATURE

Signer must equal the token holder, and the EIP-712 domain must match the extra block of the accepts entry you chose (on Base that is the Gateway Wallet contract, not the USDC contract).

400 PAYMENT_INVALID

PAYMENT-SIGNATURE is not valid base64 or does not decode to an x402 v2 payload. Make sure x402Version is 2 — v1 clients fall back to the X-PAYMENT header, which is not accepted.

Get Started

Plans & Payment

Changelog

Pay-per-call Setup

Base URL

Prerequisites

Step 0 — See the 402 challenge (no wallet needed)

TypeScript example

Python example

Cost math

Troubleshooting

​Base URL

​Prerequisites

​Step 0 — See the 402 challenge (no wallet needed)

​TypeScript example

​Python example

​Cost math

​Troubleshooting

Base URL

Prerequisites

Step 0 — See the 402 challenge (no wallet needed)

TypeScript example

Python example

Cost math

Troubleshooting