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

# x402 Integration

> Pay-per-call API access for AI Agents via the HTTP 402 protocol

## What is x402?

x402 is an open standard introduced by Coinbase. It uses the HTTP `402 Payment Required` status code to allow machines (such as AI Agents) to automatically complete on-chain micropayments when initiating API requests. Payments are made using stablecoins (like USDC), with instant, transparent settlement and no need for trusted intermediaries.

## Pricing

All Chainbase Web3 API endpoints accessed via x402 are charged at a flat rate:

|                  | Price            |
| ---------------- | ---------------- |
| **Per API Call** | **\$0.002 USDC** |

No subscriptions, no monthly fees — just pay per request with your wallet.

## Supported Endpoints

All [Chainbase Web3 API](/api-reference/overview) endpoints support x402 access. See the [API Reference](/api-reference/overview) for the complete list of available endpoints.

## Integration Steps (Python Example)

### Install Dependencies

```bash theme={null}
pip install eth_account x402
```

### Prepare Your Private Key

Please ensure you have an Ethereum wallet with sufficient USDC (it is recommended to use a testnet or mainnet cold wallet). **Never expose your real private key in public code!**

```python theme={null}
from eth_account import Account

# For production, please read from environment variables or a key management service
PRIVATE_KEY = "your_0x_private_key_here"  # Example: 0x123...abc
account = Account.from_key(PRIVATE_KEY)
```

### Initialize x402 Session

```python theme={null}
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

client = x402ClientSync()
register_exact_evm_client(client, EthAccountSigner(account))

session = x402_requests(client)
```

### Call Chainbase API

For all Chainbase Web3 API endpoints, simply add `x-api-key: x402` to the request header. The rest of the usage is consistent with the standard API.

```python theme={null}
from pprint import pprint

# Example: Query Ethereum Mainnet USDT holder addresses ($0.002 per call)
api_url = "https://api.chainbase.com/v1/token/holders?chain_id=1&contract_address=0xdac17f958d2ee523a2206206994597c13d831ec7"

headers = {
    "x-api-key": "x402",  # Enable x402 payment
    "Accept": "application/json"
}

response = session.get(api_url, headers=headers)

if response.status_code == 200:
    pprint(response.json())
else:
    print(f"Payment failed or request error: {response.status_code} - {response.text}")
```

## Use Cases

* **AI Agent automatically monitors token address changes**: Query once per hour, pay per request, no monthly fee required.
* **One-time data fetching**: Analyze a specific Token project, call only once, and pay just \$0.002.
* **Experimental development**: No need to register an enterprise account, pay directly with a wallet to test interfaces.

## Next Steps

* [API Reference](/api-reference/overview) — Full interactive API documentation
* [Supported Networks](/resources/platform/supported-networks/supported-networks) — Complete list of supported chains