402ARC

docs @ 402arc

Ship a paid endpoint
in five minutes

402ARC implements x402 v2 with the exact scheme over EIP-3009 transferWithAuthorization on Arc. The buyer signs, the seller receives USDC directly on-chain, and the facilitator verifies and broadcasts. It never holds funds, and the block it lands in is final.

1 · paywall your api

server.ts · express
// npm i 402arc-middleware express
import express from "express";
import { arc402 } from "402arc-middleware";

const app = express();

app.use("/api", arc402({
  price: "0.001",                      // USDC per request
  payTo: "0xYourAddress",              // you get paid here, directly
  network: "eip155:5042",              // Arc mainnet; eip155:5042002 for testnet
  // facilitatorUrl defaults to the hosted 402ARC facilitator
}));

app.get("/api/report", (_req, res) => res.json({ paid: true }));
app.listen(4021);

Requests without payment get an HTTP 402 with a PAYMENT-REQUIRED header. Paid responses carry a PAYMENT-RESPONSE header with the settlement tx hash.

2 · pay from code

buyer.ts · auto-paying fetch
// npm i 402arc-client
import { createSigner, payingFetch } from "402arc-client";

const pay = payingFetch({
  account: createSigner(process.env.WALLET_KEY),
  maxValue: 10_000n,        // spend cap per request: 0.01 USDC
});

const res = await pay("https://api.example.dev/report");
// 402 → signs EIP-3009 authorization → retries → 200

3 · charge agents per tool call

claude config · mcp via 402arc proxy
{
  "mcpServers": {
    "paid-tools": {
      "command": "arc402-mcp-proxy",
      "args": ["https://your-paid-mcp.example/mcp"],
      "env": {
        "ARC402_PRIVATE_KEY": "0x…",
        "ARC402_MAX_VALUE": "10000"
      }
    }
  }
}

The proxy bridges stdio MCP to your paid HTTP endpoint and settles each tool call in USDC. Handshake and tool discovery stay free. Only tools/call is billed.

network reference

NetworkCAIP-2RPCUSDC
Arc Mainneteip155:5042https://rpc.mainnet.arc.io0x3600000000000000000000000000000000000000
Arc Testneteip155:5042002https://rpc.testnet.arc.io0x3600000000000000000000000000000000000000

EIP-712 domain: name "USDC", version "2" · 6 decimals on the ERC-20 face · gas paid in the same USDC balance (18 decimals natively) · Malachite BFT with deterministic sub-second finality · 20 gwei base-fee floor. Testnet USDC for development: faucet.circle.com.

facilitator api

GET/supportedschemes + networks this facilitator services
GET/statussettlement count + native USDC gas float per network, read live from Arc
POST/verify{ paymentPayload, paymentRequirements } → { isValid, payer }
POST/settleverifies, then broadcasts transferWithAuthorization → { transaction }
GET/eventsSSE stream of verify/settle lifecycle events
GET/healthzliveness + mode

Verification checks, in order: requirement match → time window → EIP-712 signature recovery → on-chain authorization replay state and payer balance. Settlement broadcasts the buyer's signed authorization; funds move payer → payee in one transaction.

Open your lane

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