Comprehensive payment integration skill for SePay (Vietnamese payment gateway), Polar (global SaaS monetization platform), and Stripe (global payment infrastructure).

Features

SePay Integration

Vietnamese payment gateway with VietQR, NAPAS, bank transfers, and cards
44+ supported banks
Webhook verification with API Key/OAuth2 authentication
QR code generation API
Order-based virtual accounts
SDK support for Node.js, PHP, and Laravel

Polar Integration

Global SaaS monetization platform
Merchant of Record (handles global tax compliance)
Subscription management with trials, upgrades, downgrades
Usage-based billing with events and meters
Automated benefit delivery (GitHub repos, Discord roles, license keys, files)
Customer self-service portal
Multi-language SDKs (TypeScript, Python, PHP, Go)
Framework adapters (Next.js, Laravel, Remix, etc.)

Stripe Integration

Global payment infrastructure
CheckoutSessions, PaymentIntents, SetupIntents APIs
Billing and subscriptions at scale
Connect for marketplaces and platforms
Payment Element for custom checkout experiences
Multi-language SDKs (Node.js, Python, Ruby, PHP, Java, Go, .NET)
Best practices for integration design and API version upgrades

Structure

payment-integration/
├── SKILL.md                      # Main skill definition
├── README.md                     # This file
├── references/                   # Progressive disclosure documentation
│   ├── sepay/                   # SePay integration guides
│   │   ├── overview.md          # Auth, capabilities, environments
│   │   ├── api.md               # API endpoints and operations
│   │   ├── webhooks.md          # Webhook setup and handling
│   │   ├── sdk.md               # SDK usage (Node.js, PHP, Laravel)
│   │   ├── qr-codes.md          # VietQR generation
│   │   └── best-practices.md    # Security, patterns, monitoring
│   ├── polar/                   # Polar integration guides
│   │   ├── overview.md          # Auth, MoR concept, environments
│   │   ├── products.md          # Products, pricing, usage-based billing
│   │   ├── checkouts.md         # Checkout flows and embedded checkout
│   │   ├── subscriptions.md     # Lifecycle, upgrades, trials
│   │   ├── webhooks.md          # Event handling and verification
│   │   ├── benefits.md          # Automated benefit delivery
│   │   ├── sdk.md               # Multi-language SDK usage
│   │   └── best-practices.md    # Security, patterns, monitoring
│   └── stripe/                  # Stripe integration guides
│       ├── stripe-best-practices.md  # Integration design, API selection
│       └── stripe-upgrade.md         # API versions, SDK upgrades
└── scripts/                      # Integration helper scripts
    ├── sepay-webhook-verify.js   # SePay webhook verification
    ├── polar-webhook-verify.js   # Polar webhook verification
    ├── checkout-helper.js        # Checkout session generation
    ├── test-scripts.js           # Test suite for all scripts
    ├── package.json              # Node.js package configuration
    └── .env.example              # Environment variable template

Usage

Activate the Skill

Claude Code will automatically activate this skill when you mention payment integration, subscriptions, webhooks, or platform-specific terms (SePay, Polar).

Manual Activation

In conversations, simply reference the platforms:

"Implement SePay payment integration"
"Set up Polar subscriptions with usage-based billing"
"Create webhook handler for payment notifications"

Using Scripts

SePay Webhook Verification:

cd $HOME/.opencode/skills/payment-integration/scripts
node sepay-webhook-verify.js '{"id":12345,"gateway":"Vietcombank",...}'

Polar Webhook Verification:

node polar-webhook-verify.js '{"type":"order.paid","data":{...}}' base64secret

Checkout Helper:

# SePay
node checkout-helper.js sepay '{"orderInvoiceNumber":"ORD001","orderAmount":100000,...}'

# Polar
node checkout-helper.js polar '{"productPriceId":"price_xxx","successUrl":"https://..."}'

Run Tests:

npm test

Environment Variables

Copy .env.example to .env and configure:

# SePay
SEPAY_MERCHANT_ID=SP-TEST-XXXXXXX
SEPAY_SECRET_KEY=spsk_test_xxxxxxxxxxxxx
SEPAY_ENV=sandbox
SEPAY_WEBHOOK_API_KEY=your_key

# Polar
POLAR_ACCESS_TOKEN=polar_xxxxxxxxxxxxxxxx
POLAR_SERVER=sandbox
POLAR_WEBHOOK_SECRET=base64_secret

Progressive Disclosure

The skill uses progressive disclosure to minimize context usage:

SKILL.md - Overview and quick reference (~99 lines)
references/ - Detailed guides loaded as needed (<100 lines each)
scripts/ - Executable helpers with embedded examples

Load only the references you need for your current task.

Platform Selection Guide

Choose SePay for:

Vietnamese market targeting
Bank transfer automation
Local payment methods
QR code payments (VietQR/NAPAS)
Direct bank monitoring

Choose Polar for:

Global market
SaaS/subscription business
Usage-based billing
Automated benefit delivery
Tax compliance (Merchant of Record)
Customer self-service

Choose Stripe for:

Global payment infrastructure
Enterprise-grade payment processing
Connect platforms (marketplaces)
Billing/subscriptions at scale
Custom checkout experiences (Payment Element)
Maximum payment method coverage

Examples

SePay Payment Flow

Load references/sepay/overview.md for authentication
Load references/sepay/sdk.md for integration
Use checkout-helper.js to generate payment form
Load references/sepay/webhooks.md for notifications
Use sepay-webhook-verify.js to verify authenticity

Polar Subscription Flow

Load references/polar/overview.md for setup
Load references/polar/products.md for pricing
Load references/polar/checkouts.md for payment
Load references/polar/subscriptions.md for lifecycle
Load references/polar/webhooks.md for events
Load references/polar/benefits.md for automation

Stripe Integration Flow

Load references/stripe/stripe-best-practices.md for integration design
Choose: Checkout (hosted/embedded) or Payment Element
Use CheckoutSessions API for most use cases
Load references/stripe/stripe-upgrade.md when upgrading API versions

Testing

All scripts include comprehensive test coverage:

SePay webhook verification (with/without authentication)
Polar webhook signature validation
Checkout configuration generation
Error handling and edge cases

Run npm test in the scripts directory to verify functionality.

Support

License

MIT

Version

1.1.0