# I built 53 pay-per-call APIs that AI agents can pay for autonomously (x402 + USDC on Base)

> Source: <https://dev.to/laurent_halbrun_0dbdc876c/i-built-53-pay-per-call-apis-that-ai-agents-can-pay-for-autonomously-x402-usdc-on-base-11a1>
> Published: 2026-07-22 01:59:37+00:00

AI agents are getting good at *deciding* what data they need. What they're bad at is the human paperwork around getting it: creating accounts, clicking email confirmations, pasting API keys, entering a credit card. Every one of those is a wall an autonomous agent can't climb on its own.

[x402](https://www.x402.org/) removes that wall. It's an open payment protocol: the server answers `402 Payment Required`

, the client pays a few cents in USDC on-chain, and the request goes through — no account, no key, no human. So I built a farm of APIs designed to be consumed exactly that way.

**Base URL:** `https://api.x-402.online/`

— the root returns a machine-readable JSON catalog, and there's an `/openapi.json`

+ `/llms.txt`

for agents.

53 endpoints, all pay-per-call in USDC (from **$0.005**), settled on **Base** (also accepts Polygon & Arbitrum):

The friction *is* the value: these wrap sources that need signup, keys, or heavy parsing (XBRL, registries) and expose them as one clean, payable call.

``` js
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.AGENT_KEY);
const fetchPaid = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }],
});

// The wrapper handles the 402 -> sign -> retry automatically.
const res = await fetchPaid("https://api.x-402.online/v1/us/snapshot?ticker=AAPL");
console.log(await res.json());
```

The agent's wallet just needs USDC on Base. No gas needed on the client side — the facilitator settles.

Real on-chain payments are going through today (verifiable on [BaseScan](https://basescan.org/)). If you're building agents that need company data, web extraction, or open-data lookups without the account/key dance, point them at `https://api.x-402.online/`

and let them pay their own way.

Feedback welcome — happy to add endpoints agents actually ask for.