> ## Documentation Index
> Fetch the complete documentation index at: https://docs.propx402.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# x402 Protocol

> How PropX402 handles payments — no API keys, no subscriptions

## What is x402?

x402 is an open payment protocol developed by Coinbase that revives the long-reserved HTTP `402 Payment Required` status code. It enables AI agents and services to pay for API access autonomously using USDC on Base — no accounts, sessions, or human intervention required.

## Payment flow

<Steps>
  <Step title="Agent sends request">
    Your agent or app sends a normal HTTP POST to a paid endpoint. No auth header needed.
  </Step>

  <Step title="Server returns 402">
    PropX402 responds with `402 Payment Required` plus a payment payload specifying the USDC amount and Base network address.
  </Step>

  <Step title="Agent pays and retries">
    The x402 client signs and broadcasts a USDC transfer on Base mainnet, then retries the request with a payment proof header.
  </Step>

  <Step title="Server verifies and responds">
    PropX402 verifies the on-chain payment and returns the full data response.
  </Step>
</Steps>

## Why x402?

|             | Traditional API         | PropX402 (x402)  |
| ----------- | ----------------------- | ---------------- |
| Auth        | API keys, OAuth         | None required    |
| Billing     | Subscriptions, invoices | Pay per query    |
| Settlement  | Days                    | \~200ms on Base  |
| Agents      | Manual setup            | Fully autonomous |
| Chargebacks | Yes                     | Not reversible   |

## Requirements

* EVM wallet on **Base mainnet** (Coinbase Wallet, MetaMask, or any Base-compatible wallet)
* USDC balance on Base — bridge at [bridge.base.org](https://bridge.base.org) or buy directly
* x402-compatible HTTP client — [x402 SDK on GitHub](https://github.com/coinbase/x402)

## Payment receiver

All PropX402 payments settle directly to this address. No intermediaries.

```
0xCFA4F055621356974dFA4846a6e0047f593C4dDA
```

## Facilitator

```
https://x402.org/facilitator
```

## Installation

<CodeGroup>
  ```bash npm theme={null}
  npm install x402-fetch
  ```

  ```bash pip theme={null}
  pip install x402
  ```
</CodeGroup>

<Info>
  Learn more about the x402 protocol at [x402.org](https://x402.org) or read the [Coinbase x402 whitepaper](https://www.x402.org/x402-whitepaper.pdf).
</Info>