Chain ID (EIP-155)

The EIP-155 chain ID for any supported network via eth_chainId — the read multi-chain agents make to confirm which chain an RPC is on before signing. Across Base, Ethereum, Optimism, Arbitrum, Polygon, Gnosis. Free public RPC; undercuts onesource (Ethereum-only) at $0.001 on 6 chains.

Call it in 30 seconds

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

const account = privateKeyToAccount(process.env.PRIVATE_KEY); // funds USDC on Base
const wallet = createWalletClient({ account, chain: base, transport: http() });
const fetchWithPay = wrapFetchWithPayment(fetch, wallet);

// Pays the $0.001 USDC automatically on the 402, then returns the real response:
const res = await fetchWithPay("https://x402-agent-store.rileycraig14.workers.dev/chain/chain-id", { method: "GET" });
console.log(await res.json());

# pip install x402 eth-account httpx
import os, asyncio
from eth_account import Account
from x402.clients.httpx import x402HttpxClient

account = Account.from_key(os.environ["PRIVATE_KEY"])  # funds USDC on Base

async def main():
    async with x402HttpxClient(account=account) as client:
        # x402 handles the 402 -> pay ($0.001 USDC) -> retry automatically
        r = await client.get("https://x402-agent-store.rileycraig14.workers.dev/chain/chain-id")
        print((await r.aread()).decode())

asyncio.run(main())

# 1) An unpaid request returns HTTP 402 with the exact payment terms:
curl -i "https://x402-agent-store.rileycraig14.workers.dev/chain/chain-id?chain=base"

# 2) Paying + retrying requires an x402 client that can sign the USDC
#    authorization (curl alone cannot). See the JS / Python tabs below.

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