Pay from code

Pay MPP and x402 endpoints from your own application with a buyer SDK for Node.js, Python, Go, or Rust. Each SDK pays from the InFlow balance of the API key account when the seller offers it. The x402 buyer prefers the balance scheme, then exact. For the other ways to pay, see How the agent pays.

Before you start

Item	Detail
Account	An InFlow account and an API key. A Developer account can buy. A Seller account can also buy.
Environment variable	`INFLOW_API_KEY`.
Environment	The examples use the sandbox. The value must match the dashboard of the key.

When a payment needs owner approval, it waits until the owner approves it.

Pay an endpoint

Python
Go
Rust
Node.js

MPP

pip install 'inflowpay[mpp]'

The payment transport answers the 402 challenge for each request that httpx sends.

import os

import httpx

from inflowpay import ClientOptions
from inflowpay.mpp.buyer import BuyerMethod, payment_transport


async def buy(url: str) -> bytes:
    async with BuyerMethod(
        ClientOptions(environment="sandbox", api_key=os.environ["INFLOW_API_KEY"])
    ) as method:
        async with httpx.AsyncClient(transport=payment_transport([method])) as http:
            response = await http.get(url)
            response.raise_for_status()
            return response.content

x402

pip install 'inflowpay[x402]'

import asyncio
import os

import httpx
from x402.http.clients.httpx import x402AsyncTransport

from inflowpay import ClientOptions
from inflowpay.x402.buyer import Buyer


async def main():
    async with (
        await Buyer.create(
            ClientOptions(api_key=os.environ["INFLOW_API_KEY"], environment="sandbox")
        ) as buyer,
        httpx.AsyncClient(transport=x402AsyncTransport(buyer), follow_redirects=False) as http,
    ):
        response = await http.get(os.environ["PAID_RESOURCE_URL"])
        response.raise_for_status()
        print(response.text)


asyncio.run(main())

The Python SDK also supports MPP buyers over MCP. Install inflowpay[mpp,mcp].

go get github.com/inflowpayai/inflow-go@v0.3.1

The Go buyer method Do sends the request, pays a 402 challenge, and sends one paid retry. To use the challenge yourself, use Fulfil for MPP or Sign for x402.

MPP

Fulfil turns an MPP challenge into a credential.

client, err := buyer.New(buyer.Options{
    Options: inflow.Options{
        Environment: inflow.Sandbox,
        APIKey: os.Getenv("INFLOW_API_KEY"),
    },
})
if err != nil {
    return err
}
credential, err := client.Fulfil(ctx, challenge, buyer.PaymentOptions{})

x402

Sign turns the x402 payment requirements into a signed payment.

client, err := buyer.New(buyer.Options{
    Options: inflow.Options{
        Environment: inflow.Sandbox,
        APIKey: os.Getenv("INFLOW_API_KEY"),
    },
})
if err != nil {
    return err
}
payment, err := client.Sign(ctx, required, buyer.SignOptions{})

MPP

inflow-mpp-buyer uses an explicit credential workflow. The application prepares the payment, shows the approval to the owner, and waits for the credential.

use inflow_mpp_buyer::{
    Authentication, Buyer, CancellationToken, ClientOptions, Environment,
    PaymentChallenge, PaymentOptions, WaitOptions, Credential,
};

async fn approve(challenge: &PaymentChallenge) -> Result<Credential, Box<dyn std::error::Error>> {
    let buyer = Buyer::new(ClientOptions {
        environment: Environment::Sandbox,
        authentication: Authentication::ApiKey(std::env::var("INFLOW_API_KEY")?),
        ..Default::default()
    })?;
    let cancellation = CancellationToken::new();
    let payment = buyer.prepare(challenge, PaymentOptions::default(), &cancellation).await?;
    // The application can display these identifiers while approval is pending.
    let approval_id = payment.approval_id();
    let transaction_id = payment.transaction_id();
    let credential = payment.wait(WaitOptions::default()).await?;
    Ok(credential)
}

The MPP buyer supports InFlow charges, InFlow subscriptions, Tempo charges, and Visa CARD charges. For x402, use inflow-x402-buyer.

pnpm add @inflowpayai/mpp-buyer mppx@^0.8.17
pnpm add @inflowpayai/x402-buyer @x402/core

The inflow-node repository has runnable buyer examples. mpp-buyer-fetch replaces the global fetch with a payment-aware wrapper that pays a 402 response.First, start mpp-seller-express or mpp-seller-hono in a different terminal. The buyer requests http://localhost:3000/api/widgets.

cd examples/mpp-buyer-fetch
cp .env.example .env
# fill in INFLOW_API_KEY from https://sandbox.inflowpay.ai
pnpm install
pnpm start

The other buyer examples are mpp-buyer-manual, x402-buyer-fetch, and x402-buyer-axios. x402-buyer-x402-evm and x402-buyer-x402-svm use only the x402 foundation packages.

Rules for buyer code

Never log the API key or a payment credential.
Save the transaction ID as soon as you get it. You need it to check or resume a payment.
Show the approval to the owner while the payment waits.
Stripe acceptance is for sellers only. The InFlow buyer SDKs do not create Stripe tokens.

Pay with the CLI

Pay an endpoint from the command line.

SDKs

Read the packages, versions, and features of each SDK.

Overview

Pay as an agent

Integrate your service

Concepts

Reference

Before you start

Pay an endpoint

MPP

x402

MPP

x402

MPP

Rules for buyer code

Pay with the CLI

SDKs

​Before you start

​Pay an endpoint

​MPP

​x402

​MPP

​x402

​MPP

​Rules for buyer code

​Related pages

Pay with the CLI

SDKs

Before you start

Pay an endpoint

MPP

x402

MPP

x402

MPP

Rules for buyer code

Related pages