MCPInstall

web-payments

by alinaqiBackend & APIs

Stripe Checkout, subscriptions, webhooks, customer portal

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296
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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/alinaqi/maggy --skill web-payments
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads web-payments automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Web Payments Skill (Stripe)

For integrating Stripe payments into web applications - one-time payments, subscriptions, and checkout flows.

Sources: Stripe Checkout | Payment Element Best Practices | Building Solid Stripe Integrations | Subscriptions

Setup

1. Create Stripe Account

  1. Go to https://dashboard.stripe.com/register
  2. Complete business verification
  3. Get API keys from https://dashboard.stripe.com/apikeys

2. Environment Variables

# .env
STRIPE_SECRET_KEY=sk_test_xxx          # Server-side only
STRIPE_PUBLISHABLE_KEY=pk_test_xxx     # Client-side safe
STRIPE_WEBHOOK_SECRET=whsec_xxx        # For webhook verification

# Production
STRIPE_SECRET_KEY=sk_live_xxx
STRIPE_PUBLISHABLE_KEY=pk_live_xxx

3. Install SDK

# Node.js
npm install stripe @stripe/stripe-js

# Python
pip install stripe

Integration Options

MethodBest ForComplexity
Checkout (Hosted)Quick setup, Stripe-hosted pageLow
Checkout (Embedded)Custom site, embedded formLow
Payment ElementFull customization, complex flowsMedium
Custom FormComplete control (rare)High

Recommendation: Start with Checkout, migrate to Payment Element if needed.

Stripe Checkout (Recommended)

Server: Create Checkout Session

Node.js / Next.js

// app/api/checkout/route.ts (Next.js App Router)
import Stripe from "stripe";
import { NextResponse } from "next/server";

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);

export async function POST(request: Request) {
  const { priceId, mode = "payment" } = await request.json();

  try {
    const session = await stripe.checkout.sessions.create({
      mode: mode as "payment" | "subscription",
      payment_method_types: ["card"],
      line_items: [
        {
          price: priceId,
          quantity: 1,
        },
      ],
      success_url: `${process.env.NEXT_PUBLIC_URL}/success?session_id={CHECKOUT_SESSION_ID}`,
      cancel_url: `${process.env.NEXT_PUBLIC_URL}/canceled`,
      // Optional: Link to existing customer
      // customer: customerId,
      // Optional: Collect shipping
      // shipping_address_collection: { allowed_countries: ["US", "CA"] },
      // Optional: Add metadata for tracking
      metadata: {
        userId: "user_123",
        source: "pricing_page",
      },
    });

    return NextResponse.json({ sessionId: session.id, url: session.url });
  } catch (error) {
    console.error("Stripe error:", error);
    return NextResponse.json({ error: "Failed to create session" }, { status: 500 });
  }
}

Python / FastAPI

# app/api/checkout.py
import stripe
from fastapi import APIRouter, HTTPException
from pydantic import BaseModel
import os

stripe.api_key = os.environ["STRIPE_SECRET_KEY"]
router = APIRouter()

class CheckoutRequest(BaseModel):
    price_id: str
    mode: str = "payment"  # or "subscription"

@router.post("/api/checkout")
async def create_checkout_session(request: CheckoutRequest):
    try:
        session = stripe.checkout.Session.create(
            mode=request.mode,
            payment_method_types=["card"],
            line_items=[{
                "price": request.price_id,
                "quantity": 1,
            }],
            success_url=f"{os.environ['APP_URL']}/success?session_id={{CHECKOUT_SESSION_ID}}",
            cancel_url=f"{os.environ['APP_URL']}/canceled",
            metadata={
                "user_id": "user_123",
            },
        )
        return {"session_id": session.id, "url": session.url}
    except stripe.error.StripeError as e:
        raise HTTPException(status_code=400, detail=str(e))

Client: Redirect to Checkout

// components/CheckoutButton.tsx
"use client";

import { loadStripe } from "@stripe/stripe-js";

const stripePromise = loadStripe(process.env.NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY!);

export function CheckoutButton({ priceId }: { priceId: string }) {
  const handleCheckout = async () => {
    const response = await fetch("/api/checkout", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ priceId }),
    });

    const { url } = await response.json();

    // Redirect to Stripe Checkout
    window.location.href = url;
  };

  return (
    <button onClick={handleCheckout}>
      Subscribe Now
    </button>
  );
}

Embedded Checkout

For keeping users on your site:

// components/EmbeddedCheckout.tsx
"use client";

import { useEffect, useState } from "react";
import { loadStripe } from "@stripe/stripe-js";
import {
  EmbeddedCheckoutProvider,
  EmbeddedCheckout,
} from "@stripe/react-stripe-js";

const stripePromise = loadStripe(process.env.NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY!);

export function EmbeddedCheckoutForm({ priceId }: { priceId: string }) {
  const [clientSecret, setClientSecret] = useState("");

  useEffect(() => {
    fetch("/api/checkout/embedded", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ priceId }),
    })
      .then((res) => res.json())
      .then((data) => setClientSecret(data.clientSecret));
  }, [priceId]);

  if (!clientSecret) return <div>Loading...</div>;

  return (
    <EmbeddedCheckoutProvider stripe={stripePromise} options={{ clientSecret }}>
      <EmbeddedCheckout />
    </EmbeddedCheckoutProvider>
  );
}

Server endpoint for embedded:

// app/api/checkout/embedded/route.ts
export async function POST(request: Request) {
  const { priceId } = await request.json();

  const session = await stripe.checkout.sessions.create({
    mode: "subscription",
    line_items: [{ price: priceId, quantity: 1 }],
    ui_mode: "embedded",
    return_url: `${process.env.NEXT_PUBLIC_URL}/success?session_id={CHECKOUT_SESSION_ID}`,
  });

  return NextResponse.json({ clientSecret: session.client_secret });
}

Webhooks (Critical)

Never trust client-side data. Always verify payments via webhooks.

Webhook Endpoint

// app/api/webhooks/stripe/route.ts
import Stripe from "stripe";
import { headers } from "next/headers";

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
const webhookSecret = process.env.STRIPE_WEBHOOK_SECRET!;

export async function POST(request: Request) {
  const body = await request.text();
  const signature = headers().get("stripe-signature")!;

  let event: Stripe.Event;

  // Verify webhook signature
  try {
    event = stripe.webhooks.constructEvent(body, signature, webhookSecret);
  } catch (err) {
    console.error("Webhook signature verification failed");
    return new Response("Invalid signature", { status: 400 });
  }

  // Handle events
  switch (event.type) {
    case "checkout.session.completed": {
      const session = event.data.object as Stripe.Checkout.Session;
      await handleCheckoutComplete(session);
      break;
    }
    case "customer.subscription.created":
    case "customer.subscription.updated": {
      const subscription = event.data.object as Stripe.Subscription;
      await handleSubscriptionUpdate(subscription);
      break;
    }
    case "customer.subscription.deleted": {
      const subscription = event.data.object as Stripe.Subscription;
      await handleSubscriptionCanceled(subscription);
      break;
    }
    case "invoice.payment_failed": {
      const invoice = event.data.object as Stripe.Invoice;
      await handlePaymentFailed(invoice);
      break;
    }
    default:
      console.log(`Unhandled event type: ${event.type}`);
  }

  // Return 200 quickly - process async if needed
  return new Response("OK", { status: 200 });
}

async function handleCheckoutComplete(session: Stripe.Checkout.Session) {
  const userId = session.metadata?.userId;
  const customerId = session.customer as string;
  const subscriptionId = session.subscription as string;

  // Update your database
  await db.user.update({
    where: { id: userId },
    data: {
      stripeCustomerId: customerId,
      stripeSubscriptionId: subscriptionId,
      subscriptionStatus: "active",
    },
  });
}

Python Webhook

# app/api/webhooks.py
import stripe
from fastapi import APIRouter, Request, HTTPException

router = APIRouter()

@router.post("/api/webhooks/stripe")
async def stripe_webhook(request: Request):
    payload = await request.body()
    sig_header = request.headers.get("stripe-signature")

    try:
        event = stripe.Webhook.construct_event(
            payload, sig_header, os.environ["STRIPE_WEBHOOK_SECRET"]
        )
    except ValueError:
        raise HTTPException(status_code=400, detail="Invalid payload")
    except stripe.error.SignatureVerificationError:
        raise HTTPException(status_code=400, detail="Invalid signature")

    # Handle events
    if event["type"] == "checkout.session.completed":
        session = event["data"]["object"]
        await handle_checkout_complete(session)
    elif event["type"] == "customer.subscription.deleted":
        subscription = event["data"]["object"]
        await handle_subscription_canceled(subscription)

    return {"status": "success"}

Key Webhook Events

EventWhenAction
checkout.session.completedPayment successfulProvision access
customer.subscription.createdNew subscriptionStore subscription ID
customer.subscription.updatedPlan changeUpdate plan in DB
customer.subscription.deletedCanceledRevoke access
invoice.payment_failedPayment failedNotify user, retry
invoice.paidRenewal successfulExtend access

Products & Prices

Create via Dashboard (Recommended)

  1. Go to https://dashboard.stripe.com/products
  2. Create product with name, description
  3. Add price(s) - one-time or recurring
  4. Copy Price ID (price_xxx)

Create via API

// One-time product
const product = await stripe.products.create({
  name: "Pro Plan",
  description: "Full access to all features",
});

const price = await stripe.prices.create({
  product: product.id,
  unit_amount: 2999, // $29.99 in cents
  currency: "usd",
});

// Subscription product
const subscriptionPrice = await stripe.prices.create({
  product: product.id,
  unit_amount: 999, // $9.99/month
  currency: "usd",
  recurring: {
    interval: "month",
  },
});

Customer Portal

Let users manage their subscriptions:

// app/api/portal/route.ts
export async function POST(request: Request) {
  const { customerId } = await request.json();

  const session = await stripe.billingPortal.sessions.create({
    customer: customerId,
    return_url: `${process.env.NEXT_PUBLIC_URL}/settings`,
  });

  return NextResponse.json({ url: session.url });
}

Configure portal at: https://dashboard.stripe.com/settings/billing/portal

Subscriptions

Create Subscription with Trial

const session = await stripe.checkout.sessions.create({
  mode: "subscription",
  line_items: [{ price: priceId, quantity: 1 }],
  subscription_data: {
    trial_period_days: 14,
    // Cancel if no payment method after trial
    trial_settings: {
      end_behavior: { missing_payment_method: "cancel" },
    },
  },
  success_url: successUrl,
  cancel_url: cancelUrl,
});

Check Subscription Status

// lib/subscription.ts
export async function getSubscriptionStatus(customerId: string) {
  const subscriptions = await stripe.subscriptions.list({
    customer: customerId,
    status: "all",
    limit: 1,
  });

  if (subscriptions.data.length === 0) {
    return { status: "none", plan: null };
  }

  const subscription = subscriptions.data[0];
  return {
    status: subscription.status,
    plan: subscription.items.data[0].price.id,
    currentPeriodEnd: new Date(subscription.current_period_end * 1000),
    cancelAtPeriodEnd: subscription.cancel_at_period_end,
  };
}

Testing

Test Cards

Card NumberScenario
4242424242424242Success
4000000000000002Declined
4000002500003155Requires 3D Secure
4000000000009995Insufficient funds

Stripe CLI for Webhooks

# Install CLI
brew install stripe/stripe-cli/stripe

# Login
stripe login

# Forward webhooks to local server
stripe listen --forward-to localhost:3000/api/webhooks/stripe

# Trigger test events
stripe trigger checkout.session.completed
stripe trigger customer.subscription.deleted

Project Structure

project/
├── app/
│   ├── api/
│   │   ├── checkout/
│   │   │   └── route.ts          # Create checkout session
│   │   ├── portal/
│   │   │   └── route.ts          # Customer portal
│   │   └── webhooks/
│   │       └── stripe/
│   │           └── route.ts      # Webhook handler
│   ├── pricing/
│   │   └── page.tsx              # Pricing page
│   ├── success/
│   │   └── page.tsx              # Post-checkout success
│   └── settings/
│       └── page.tsx              # Manage subscription
├── lib/
│   ├── stripe.ts                 # Stripe client
│   └── subscription.ts           # Subscription helpers
└── .env.local

Security Best Practices

Non-Negotiable Rules

  1. Server-side only for secrets - Never expose STRIPE_SECRET_KEY
  2. Always verify webhooks - Check signature before processing
  3. Idempotency - Store webhook event IDs, skip duplicates
  4. Use metadata - Track user IDs, sources for debugging
  5. Handle all states - Success, failure, pending, canceled

Idempotent Webhook Handler

const processedEvents = new Set<string>(); // Use Redis in production

export async function POST(request: Request) {
  // ... verify signature ...

  // Skip duplicate events
  if (processedEvents.has(event.id)) {
    return new Response("Already processed", { status: 200 });
  }
  processedEvents.add(event.id);

  // Process event...
}

Amount Handling

// Always use cents (smallest currency unit)
const priceInCents = 2999; // $29.99

// Helper functions
const toCents = (dollars: number) => Math.round(dollars * 100);
const toDollars = (cents: number) => cents / 100;

// Display
const displayPrice = (cents: number) =>
  new Intl.NumberFormat("en-US", {
    style: "currency",
    currency: "USD",
  }).format(toDollars(cents));

Common Patterns

Pricing Page

// app/pricing/page.tsx
const plans = [
  {
    name: "Starter",
    price: "$9/mo",
    priceId: "price_starter_monthly",
    features: ["Feature 1", "Feature 2"],
  },
  {
    name: "Pro",
    price: "$29/mo",
    priceId: "price_pro_monthly",
    features: ["Everything in Starter", "Feature 3", "Feature 4"],
    popular: true,
  },
];

export default function PricingPage() {
  return (
    <div className="grid md:grid-cols-2 gap-8">
      {plans.map((plan) => (
        <div key={plan.name} className={plan.popular ? "border-blue-500" : ""}>
          <h3>{plan.name}</h3>
          <p>{plan.price}</p>
          <ul>
            {plan.features.map((f) => <li key={f}>{f}</li>)}
          </ul>
          <CheckoutButton priceId={plan.priceId} />
        </div>
      ))}
    </div>
  );
}

Protect Routes by Subscription

// middleware.ts
import { getSubscriptionStatus } from "@/lib/subscription";

export async function middleware(request: NextRequest) {
  const session = await getSession();

  if (request.nextUrl.pathname.startsWith("/pro")) {
    const { status } = await getSubscriptionStatus(session.stripeCustomerId);

    if (status !== "active" && status !== "trialing") {
      return NextResponse.redirect(new URL("/pricing", request.url));
    }
  }
}

Anti-Patterns

  • Hardcoding API keys - Use environment variables
  • Client-side payment creation - Always create PaymentIntent/Session server-side
  • Skipping webhook verification - Always verify signatures
  • Processing duplicate webhooks - Implement idempotency
  • Floating-point currency math - Use integers (cents)
  • Trusting client data - Verify everything server-side
  • Ignoring failed payments - Handle invoice.payment_failed
  • No error handling - Catch and handle Stripe errors

Quick Reference

# Install
npm install stripe @stripe/stripe-js @stripe/react-stripe-js

# Stripe CLI
stripe login
stripe listen --forward-to localhost:3000/api/webhooks/stripe
stripe trigger checkout.session.completed

# Test mode prefix
sk_test_xxx  # Secret key
pk_test_xxx  # Publishable key

# Live mode prefix
sk_live_xxx
pk_live_xxx

Key Endpoints

EndpointPurpose
POST /api/checkoutCreate checkout session
POST /api/portalCustomer billing portal
POST /api/webhooks/stripeHandle Stripe events

Environment Variables

STRIPE_SECRET_KEY=sk_test_xxx
STRIPE_PUBLISHABLE_KEY=pk_test_xxx
STRIPE_WEBHOOK_SECRET=whsec_xxx
NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY=pk_test_xxx

FAQ

What does the web-payments skill do?

Stripe Checkout, subscriptions, webhooks, customer portal

How do I install web-payments?

Run npx skills add https://github.com/alinaqi/maggy --skill web-payments in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/web-payments/ (personal) or .claude/skills/web-payments/ (project).

Which AI agents can use web-payments?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is web-payments safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains web-payments?

It is published by alinaqi in alinaqi/maggy. It has 296 recorded installs.

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