Payable to bearer, on demand.

Scip settles a stablecoin payment inside the request that asks for it. The price arrives in a response header and the money moves before the body does — no account, no invoice, no checkout.

Price a route See the exchange

HTTP/1.1 402 Payment Required
pay-to: 0x7A3f…9C21
chain: robinhood-mainnet

0.0100 USDCNo. 0000 0000

GET /v1/quote
0.0020 USDC
POST /v1/backtest
0.2500 USDC
GET /v1/filings
0.0500 USDC
POST /v1/transcribe
0.0400 USDC
GET /v1/orderbook
0.0015 USDC
POST /v1/embed
0.0008 USDC

Example routes. One stub is green: the request being paid for right now.

Four messages, one round trip

x402 turns payment into a handshake. Nothing is stored between the two requests, so a caller that has never seen your API before can pay it on first contact.

1
client
Ask, without paying
A caller requests the resource the ordinary way. It does not need to know the price yet, or hold an account.
```
GET /v1/quote?symbol=HOOD HTTP/1.1
host: api.example.com
```

server

Quote the price

The server answers 402 and names its terms: the amount, the asset, the address to pay, and the chain to pay it on.

HTTP/1.1 402 Payment Required
content-type: application/json

{ "x402Version": 1,
  "accepts": [{
    "scheme": "exact",
    "network": "robinhood",
    "maxAmountRequired": "2000",
    "payTo": "0x7A3f…9C21"
  }] }

3
client
Sign and retry
The caller signs a transfer authorization for exactly that amount and repeats the request with the signature attached. It never sends a private key, and never more than the quote.
```
GET /v1/quote?symbol=HOOD HTTP/1.1
x-payment: eyJzY2hlbWUiOiJleGFjdCIsInBheWxvYWQ…
```
4
server, then facilitator
Verify, answer, settle
Scip checks the signature, lets the route run, then submits the transfer on Robinhood Chain and returns the receipt beside the response body.
```
HTTP/1.1 200 OK
x-payment-response: eyJzdWNjZXNzIjp0cnVlLCJ0eEhhc2gi…
content-type: application/json
```

Why this rail

A per-request payment only works if confirming it costs less than the thing being sold, and takes less time than serving it.

100 ms: Robinhood Chain block time. A payment can confirm inside the same round trip that asked for the resource.
402: The status code HTTP reserved for payment in 1997 and left undefined. x402 is the definition that arrived.
1 header: What a server adds to start charging. No checkout page, no billing portal, no invoices to reconcile later.

Price a route

Two changes: one on the server that quotes, one on the client that pays. Everything between them is the ordinary request you already have.

On the server

import { paywall } from "@scip/x402";

export const middleware = paywall({
  network: "robinhood",
  payTo: process.env.SCIP_PAYEE,
  routes: {
    "/v1/quote": "0.0020",
    "/v1/backtest": "0.2500",
  },
});

export const config = { matcher: "/v1/:path*" };

On the client

import { withPayment } from "@scip/x402/client";

const pay = withPayment(fetch, {
  signer,
  maxPerCall: "0.05",
});

// Reads the 402, signs, retries once.
const res = await pay(
  "https://api.example.com/v1/quote?symbol=HOOD"
);