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

# x402 Overview

> Access GoldRush blockchain data APIs with pay-per-call micropayments. No API key, no signup, no billing - just a wallet.

GoldRush x402 lets you access the full GoldRush blockchain data API by paying per request using the [x402 protocol](https://x402.org). No account, no API key, no billing page - just pay for exactly what you use, directly from a wallet.

<Info>
  GoldRush x402 is live on **Base Sepolia testnet**. Mainnet support is coming soon.
</Info>

## What is x402?

HTTP status code `402 Payment Required` has existed since 1997, reserved for "future use." The [x402 protocol](https://x402.org) makes it real - enabling native payments over HTTP using stablecoins.

When you call a GoldRush x402 endpoint without payment, the server responds with `402 Payment Required` along with payment instructions. Your client pays using stablecoins on Base, retries the request with proof of payment, and gets the data - all in a single request-response cycle.

## How it works

GoldRush x402 is a transparent reverse proxy in front of `api.covalenthq.com`. It exposes the same paths and returns the same responses - the only difference is how you authenticate. Instead of an API key, you attach a micropayment.

```
Your App -- x402 payment --> GoldRush x402 Proxy --> api.covalenthq.com
                                    |
                              validates request
                              verifies payment
                              caches response
                              returns data
```

The proxy validates your request **before** charging you. If the chain doesn't exist, the address is malformed, or the endpoint doesn't support that network - you get a clear error and pay nothing.

## What's supported

* **60+ endpoints** covering balances, NFTs, transactions, blocks, DEX data, pricing, security, and cross-chain operations
* **100+ blockchain networks** including Ethereum, Base, Arbitrum, Optimism, Polygon, Solana, Bitcoin, and more
* **Response caching** with intelligent TTLs (30s for balances, 5m for pricing data) - cached responses cost less
* **Per-wallet rate limiting** at 100 requests per minute
* **Request validation** before payment - you never pay for a request that would fail

## Pricing

Every endpoint has a credit rate. The price per call is:

```
Price = creditRate x $0.000001
```

### Fixed pricing

Most endpoints have a fixed cost per request. Token balances, NFT holdings, block details - one price, one call, one response.

### Dynamic pricing

Endpoints that return variable-length data (transaction histories, event logs) use tiered pricing. You select a tier upfront based on how much data you expect:

| Tier   | Items   | You pay for ... |
| ------ | ------- | --------------- |
| Small  | 1-50    | 50 items        |
| Medium | 51-200  | 200 items       |
| Large  | 201-500 | 500 items       |
| XL     | 501+    | 1000 items      |

If the response contains fewer items than your tier covers, you overpaid slightly but get the data immediately. If it contains more, you get a `402` telling you exactly which tier you need.

## x402 vs API key

<CardGroup cols={2}>
  <Card title="x402 (Pay-per-call)" icon="wallet">
    * No signup or account needed
    * Pay per request with a wallet
    * Ideal for AI agents and autonomous workflows
    * Live on Base Sepolia testnet
  </Card>

  <Card title="API Key (Subscription)" icon="key">
    * Predictable monthly cost
    * API key for any project
    * Ideal for apps with steady usage
    * For Vibe Coders or Teams
  </Card>
</CardGroup>

Both paths give you the same data, the same endpoints, and the same response format. Pick the one that fits how you build.