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What it is

Nanopayment is one of two ways to pay for Arrays data — the other is a subscription. Instead of a plan and an API key, your code or AI agent calls our API and pays per request in stablecoins using the x402 HTTP standard (v2). Two settlement rails are live:
  • Base — USDC via Circle Gateway (Nanopayments)
  • BNB Chain — USDC, USDT, USD1, or United Stables via EIP-3009 or Permit2
It works across both integration methods: call it directly from the REST API, or let an agent using Skills pay as it goes. No subscription. No API key. No procurement.
Read the launch blog: Arrays Financial Data launches on Nanopayments, powered by Circle Gateway.

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Base URL

Nanopayment runs on a dedicated host:
Same paths, same responses as the API-key host — but on this host a plain GET to any priced endpoint returns 402 Payment Required instead of 401, which is what standard x402 clients expect.
The API-key host data-tools.prd.arrays.org also speaks x402 if you add the request header Accept-Payment: x402. Without that header it returns 401 — stock x402 SDKs send a bare GET, so point them at the x402 host above.

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How it works

1

Your client calls an Arrays endpoint on the x402 host

Plain GET, no auth header needed.
2

The server returns HTTP 402 Payment Required

The PAYMENT-REQUIRED response header carries a base64 x402 v2 payload: { x402Version: 2, accepts: [...], resource }. Each accepts entry is one payment option (network, asset, amount, payTo). The same JSON is echoed in the body.
3

Your wallet signs an authorization

EIP-3009 TransferWithAuthorization (Base via Circle Gateway, or BNB Chain) or a Permit2 signature (BNB Chain). Off-chain signature — no gas, no transaction broadcast.
4

Client retries with the signature

Send the signed payload in the PAYMENT-SIGNATURE header. Arrays settles with the facilitator and returns the data; the settlement result is in the PAYMENT-RESPONSE header.
Verify the 402 challenge without a wallet:

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Supported chains & assets

Amounts in the 402 are in the asset’s smallest unit: 6 decimals on Base USDC (8000 = $0.008), 18 decimals on BNB Chain (8000000000000000 = $0.008). Read them from the response — don’t hard-code prices. Deposits for the Base rail go through Circle Gateway, which pools USDC from 11 EVM chains into one balance.

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Pricing (today)

Nanopayment currently covers 15 crypto endpoints. Stocks, ETF, macro, and options are planned for the next two quarters.
Any other route called with x402 headers returns 404 X402_NOT_SUPPORTED. On the x402 host, these 15 routes always return 402 — an X-API-Key header is ignored there; use the API-key host for subscription access.

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When to use it

✅ Perfect for

  • Autonomous AI agents that pay for their own data
  • Burst / low-volume usage where a subscription is overkill
  • On-chain native projects already holding USDC or BNB Chain stablecoins
  • Prototyping without account creation

❌ Not ideal for

  • Stock / ETF / macro queries (not yet supported)
  • High-volume usage where Pro subscription is cheaper
  • Teams that need a dashboard, usage analytics, or SLAs

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Next step

Build your first paid call

TypeScript end-to-end example in under 30 lines.