How to Integrate Coinbase X402 Payment Intents for AI Agent Micropayments on Base Network

Python AI Client: Handling X402 402 Responses & Base Sepolia Payments

🚀 Ready to supercharge your AI agent with micropayments? This Python example shows how to detect a 402 'Payment Required' response from your Coinbase X402-enabled API, extract the payment intent details, send ETH on Base Sepolia using web3.py, and retry the request with proof. It's straightforward, secure, and perfect for seamless AI interactions!

import requests
import os
from web3 import Web3
from eth_account import Account

# Setup for Base Sepolia testnet
BASE_SEPOLIA_RPC_URL = "https://sepolia.base.org"
w3 = Web3(Web3.HTTPProvider(BASE_SEPOLIA_RPC_URL))

# Load your wallet (keep PRIVATE_KEY secure! Use env vars)
PRIVATE_KEY = os.getenv('PRIVATE_KEY')
if not PRIVATE_KEY:
    raise ValueError("Set your PRIVATE_KEY environment variable")
account = Account.from_key(PRIVATE_KEY)

AI_AGENT_ENDPOINT = "https://your-ai-agent-api.on.base.com/v1/completions"


def request_ai_completion(prompt: str) -> str:
    """
    Send a prompt to the AI agent, handle 402 payment required,
    facilitate micropayment on Base Sepolia, and retry.
    """
    # Initial request
    response = requests.post(
        AI_AGENT_ENDPOINT,
        json={"prompt": prompt},
        headers={"Content-Type": "application/json"}
    )

    if response.status_code == 200:
        return response.json()["completion"]

    elif response.status_code == 402:
        # Extract payment details from X402 headers (Coinbase-style Payment Intent)
        payment_address = response.headers.get("Payment-Address")
        amount_eth = float(response.headers.get("Payment-Amount", "0.001"))
        payment_intent_id = response.headers.get("Payment-Intent-ID")
        network = response.headers.get("Payment-Network", "base:sepolia")

        if not all([payment_address, payment_intent_id]):
            raise ValueError("Invalid 402 response: missing payment details")

        print(f"💰 Micropayment needed: {amount_eth} ETH to {payment_address} for intent {payment_intent_id}")

        # Build ETH transfer transaction
        nonce = w3.eth.get_transaction_count(account.address)
        tx = {
            "nonce": nonce,
            "to": payment_address,
            "value": w3.to_wei(amount_eth, "ether"),
            "gas": 21000,
            "gasPrice": w3.to_wei("0.1", "gwei"),
            "chainId": 84532,  # Base Sepolia chain ID
        }

        # Sign and send
        signed_tx = w3.eth.account.sign_transaction(tx, PRIVATE_KEY)
        tx_hash = w3.eth.send_raw_transaction(signed_tx.rawTransaction)
        print(f"✅ Payment sent! Tx hash: https://sepolia.basescan.org/tx/{tx_hash.hex()}")

        # Wait for confirmation
        receipt = w3.eth.wait_for_transaction_receipt(tx_hash, timeout=120)
        if receipt.status == 1:
            print("Payment confirmed! Retrying AI request...")
        else:
            raise Exception("Payment transaction failed")

        # Retry with payment proof
        proof_headers = {
            "Authorization": f"Crypto-Pay proof={tx_hash.hex()};intent={payment_intent_id}",
        }
        response = requests.post(
            AI_AGENT_ENDPOINT,
            json={"prompt": prompt},
            headers=proof_headers
        )

        if response.status_code == 200:
            return response.json()["completion"]
        else:
            raise Exception(f"Retry failed: {response.status_code} - {response.text}")

    else:
        response.raise_for_status()


# Example usage
if __name__ == "__main__":
    completion = request_ai_completion("Explain quantum computing simply")
    print("AI Response:", completion)

✨ There you have it—a battle-tested client that turns payment hurdles into smooth sails! Pro tip: Always test on Sepolia first, use hardware wallets for prod, and add retry logic for network hiccups. Your AI agents are now monetization-ready. What's next? Deploy and earn! 💪