Quickstart — add payments to an AI agent with PayPack

Install langchain-paypack and give an agent the ability to pay. PayPack exposes one payment call and hides the differences between on-chain (x402 / AP2) and fiat (Alipay, WeChat Pay) rails behind it.

Requirements

Step 1 — Install

pip install langchain-paypack

If you are in mainland China, the Gitee mirror is usually faster:

pip install https://gitee.com/rhcjw_com/paypack/raw/master/dist/langchain_paypack-0.5.0-py3-none-any.whl

Step 2 — Choose a rail

Step 3a — Pay with Alipay (CNY)

from paypack import AgentPay
from paypack.signer.alipay import AlipaySigner

signer = AlipaySigner(
    app_id="your-app-id",
    private_key_path="key.pem",
    alipay_public_key_path="alipay_public_key.pem",
    sandbox=True,               # set False for production
)
pay = AgentPay(signer=signer, network="alipay")

receipt = pay.send(
    to="user_alipay_id",
    amount=0.01,
    currency="CNY",
    subject="AI data subscription",
)
print(receipt)

Web checkout (QR code)

pay_url = signer.page_pay(
    out_trade_no="ORDER_20261020_001",
    total_amount=9.90,
    subject="AI Agent API monthly fee",
    body="Generated by PayPack",
)
# Open pay_url in a browser; the user scans the QR to pay.

Step 3b — Pay with WeChat Pay (CNY)

from paypack_wechat import WechatSigner
from paypack import AgentPay

signer = WechatSigner(
    mchid="merchant-id",
    serial_no="certificate-serial",
    private_key_path="apiclient_key.pem",
    api_v3_key="api-v3-key",
    license_key="PAYPACK-WECHAT-v1-...",
    app_id="mini-program-appid",
    notify_url="https://your-domain.com/wechat/notify",
)
pay = AgentPay(signer=signer, network="wechat")

result = pay.send(
    to="user-openid",
    amount=9.90,
    currency="CNY",
    subject="AI monthly subscription",
    app_id="mini-program-appid",
)
# result["prepay_params"] is passed to the frontend (wx.requestPayment).

Step 3c — Pay on-chain with x402 (USDC / ETH)

from paypack import AgentPay
import requests

pay = AgentPay(
    wallet_config={"private_key": "0x..."},
    network="base-sepolia",
    spend_limit_daily=10.0,      # safety fuse
)

# The merchant API answers 402 with a payment requirement
response = requests.get("https://api.example.com/premium")
if response.status_code == 402:
    content = pay.auto_handle_402(response)

# Or send directly
receipt = pay.send(to="0xRecipientAddress", amount=0.001, currency="USDC")
print(receipt["tx_hash"])

Step 4 — Use it as a LangChain tool

from langchain_paypack import PayPackTool

tool = PayPackTool(
    private_key="0x...",
    wallet_address="0x...",
    network="base-sepolia",
    spend_limit_daily=10.0,
)

result = tool._run(to="0x...", amount=0.001, currency="USDC")

Register the tool on your agent and the model can call it like any other tool.

Step 5 (optional) — Use the hosted Cloud API instead

If you do not want to manage merchant keys, PayPack Cloud exposes a plain HTTP API:

# Register and get an API key
curl -X POST https://rhcjw.com/pay/v1/register \
  -H "Content-Type: application/json" \
  -d '{"name":"myapp","email":"user@example.com"}'

# Create a payment
curl -X POST https://rhcjw.com/pay/v1/pay \
  -H "Authorization: Bearer ppk_xxx" \
  -H "Content-Type: application/json" \
  -d '{"amount":0.01,"subject":"AI service","channel":"alipay"}'

Supported networks

Verification status

Safety features you get by default

• Daily spend limit — spend_limit_daily caps what the agent can spend in 24 hours.
• Balance check — payments fail fast if the wallet lacks funds.
• Auditable receipts — every payment returns a receipt with a transaction hash or provider order id.
• Signer abstraction — swap a local key for AWS KMS in production without changing agent code.

PayPack is a developer tool for payment integration. It does not provide investment services, does not promise returns, and does not hold user funds.
Operated by Xiamen Shizhun Technology Co., Ltd. (Unified Social Credit Code: 91350211MA34XHGG5T) · Website: rhcjw.com · ICP filing: 闽ICP备2024041817号-2