PayPal Integration

Overview

This public intake copy packages

plugins/antigravity-awesome-skills-claude/skills/paypal-integration

https://github.com/sickn33/antigravity-awesome-skills

Use it when the operator needs the upstream workflow, support files, and repository context to stay intact while the public validator and private enhancer continue their normal downstream flow.

This intake keeps the copied upstream files intact and uses

metadata.json

ORIGIN.md

PayPal Integration Master PayPal payment integration including Express Checkout, IPN handling, recurring billing, and refund workflows.

Imported source sections that did not map cleanly to the public headings are still preserved below or in the support files. Notable imported sections: Core Concepts, Express Checkout Implementation, IPN (Instant Payment Notification) Handling, Subscription/Recurring Billing, Error Handling, Testing.

When to Use This Skill

Use this section as the trigger filter. It should make the activation boundary explicit before the operator loads files, runs commands, or opens a pull request.

• The task is unrelated to paypal integration
• You need a different domain or tool outside this scope
• Integrating PayPal as a payment option
• Implementing express checkout flows
• Setting up recurring billing with PayPal
• Processing refunds and payment disputes

Operating Table

metadata.json

ORIGIN.md

SKILL.md

SKILL.md

## Related Skills

Workflow

This workflow is intentionally editorial and operational at the same time. It keeps the imported source useful to the operator while still satisfying the public intake standards that feed the downstream enhancer flow.

1. Clarify goals, constraints, and required inputs.
2. Apply relevant best practices and validate outcomes.
3. Provide actionable steps and verification.
4. If detailed examples are required, open resources/implementation-playbook.md.
5. Confirm the user goal, the scope of the imported workflow, and whether this skill is still the right router for the task.
6. Read the overview and provenance files before loading any copied upstream support files.
7. Load only the references, examples, prompts, or scripts that materially change the outcome for the current request.

Imported Workflow Notes

Imported: Instructions

• Clarify goals, constraints, and required inputs.
• Apply relevant best practices and validate outcomes.
• Provide actionable steps and verification.
• If detailed examples are required, open

  resources/implementation-playbook.md

  .

Imported: Refund Workflows

def create_refund(capture_id, amount=None, note=None):
    """Create a refund for a captured payment."""
    client = PayPalClient(CLIENT_ID, CLIENT_SECRET)

    url = f"{client.base_url}/v2/payments/captures/{capture_id}/refund"
    headers = {
        "Content-Type": "application/json",
        "Authorization": f"Bearer {client.access_token}"
    }

    payload = {}
    if amount:
        payload["amount"] = {
            "value": str(amount),
            "currency_code": "USD"
        }

    if note:
        payload["note_to_payer"] = note

    response = requests.post(url, headers=headers, json=payload)
    return response.json()

def get_refund_details(refund_id):
    """Get refund details."""
    client = PayPalClient(CLIENT_ID, CLIENT_SECRET)

    url = f"{client.base_url}/v2/payments/refunds/{refund_id}"
    headers = {
        "Authorization": f"Bearer {client.access_token}"
    }

    response = requests.get(url, headers=headers)
    return response.json()

Imported: Core Concepts

1. Payment Products

PayPal Checkout

• One-time payments
• Express checkout experience
• Guest and PayPal account payments

PayPal Subscriptions

• Recurring billing
• Subscription plans
• Automatic renewals

PayPal Payouts

• Send money to multiple recipients
• Marketplace and platform payments

2. Integration Methods

Client-Side (JavaScript SDK)

• Smart Payment Buttons
• Hosted payment flow
• Minimal backend code

Server-Side (REST API)

• Full control over payment flow
• Custom checkout UI
• Advanced features

3. IPN (Instant Payment Notification)

• Webhook-like payment notifications
• Asynchronous payment updates
• Verification required

Examples

Example 1: Ask for the upstream workflow directly

Use @paypal-integration to handle <task>. Start from the copied upstream workflow, load only the files that change the outcome, and keep provenance visible in the answer.

Explanation: This is the safest starting point when the operator needs the imported workflow, but not the entire repository.

Example 2: Ask for a provenance-grounded review

Review @paypal-integration against metadata.json and ORIGIN.md, then explain which copied upstream files you would load first and why.

Explanation: Use this before review or troubleshooting when you need a precise, auditable explanation of origin and file selection.

Example 3: Narrow the copied support files before execution

Use @paypal-integration for <task>. Load only the copied references, examples, or scripts that change the outcome, and name the files explicitly before proceeding.

Explanation: This keeps the skill aligned with progressive disclosure instead of loading the whole copied package by default.

Example 4: Build a reviewer packet

Review @paypal-integration using the copied upstream files plus provenance, then summarize any gaps before merge.

Explanation: This is useful when the PR is waiting for human review and you want a repeatable audit packet.

Imported Usage Notes

Imported: Quick Start

// Frontend - PayPal Smart Buttons
<div id="paypal-button-container"></div>

<script src="https://www.paypal.com/sdk/js?client-id=YOUR_CLIENT_ID&currency=USD"></script>
<script>
  paypal.Buttons({
    createOrder: function(data, actions) {
      return actions.order.create({
        purchase_units: [{
          amount: {
            value: '25.00'
          }
        }]
      });
    },
    onApprove: function(data, actions) {
      return actions.order.capture().then(function(details) {
        // Payment successful
        console.log('Transaction completed by ' + details.payer.name.given_name);

        // Send to backend for verification
        fetch('/api/paypal/capture', {
          method: 'POST',
          headers: {'Content-Type': 'application/json'},
          body: JSON.stringify({orderID: data.orderID})
        });
      });
    }
  }).render('#paypal-button-container');
</script>

# Backend - Verify and capture order
from paypalrestsdk import Payment
import paypalrestsdk

paypalrestsdk.configure({
    "mode": "sandbox",  # or "live"
    "client_id": "YOUR_CLIENT_ID",
    "client_secret": "YOUR_CLIENT_SECRET"
})

def capture_paypal_order(order_id):
    """Capture a PayPal order."""
    payment = Payment.find(order_id)

    if payment.execute({"payer_id": payment.payer.payer_info.payer_id}):
        # Payment successful
        return {
            'status': 'success',
            'transaction_id': payment.id,
            'amount': payment.transactions[0].amount.total
        }
    else:
        # Payment failed
        return {
            'status': 'failed',
            'error': payment.error
        }

Best Practices

Treat the generated public skill as a reviewable packaging layer around the upstream repository. The goal is to keep provenance explicit and load only the copied source material that materially improves execution.

• Always Verify IPN: Never trust IPN without verification
• Idempotent Processing: Handle duplicate IPN notifications
• Error Handling: Implement robust error handling
• Logging: Log all transactions and errors
• Test Thoroughly: Use sandbox extensively
• Webhook Backup: Don't rely solely on client-side callbacks
• Currency Handling: Always specify currency explicitly

Imported Operating Notes

Imported: Best Practices

1. Always Verify IPN: Never trust IPN without verification
2. Idempotent Processing: Handle duplicate IPN notifications
3. Error Handling: Implement robust error handling
4. Logging: Log all transactions and errors
5. Test Thoroughly: Use sandbox extensively
6. Webhook Backup: Don't rely solely on client-side callbacks
7. Currency Handling: Always specify currency explicitly

Troubleshooting

Problem: The operator skipped the imported context and answered too generically

Symptoms: The result ignores the upstream workflow in

plugins/antigravity-awesome-skills-claude/skills/paypal-integration

metadata.json

ORIGIN.md

Problem: The imported workflow feels incomplete during review

Symptoms: Reviewers can see the generated

SKILL.md

Problem: The task drifted into a different specialization

Symptoms: The imported skill starts in the right place, but the work turns into debugging, architecture, design, security, or release orchestration that a native skill handles better. Solution: Use the related skills section to hand off deliberately. Keep the imported provenance visible so the next skill inherits the right context instead of starting blind.

Related Skills

• @00-andruia-consultant-v2

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

• @10-andruia-skill-smith-v2

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

• @20-andruia-niche-intelligence-v2

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

• @2d-games

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

Additional Resources

Use this support matrix and the linked files below as the operator packet for this imported skill. They should reflect real copied source material, not generic scaffolding.

references

references/n/a

examples

examples/n/a

scripts

scripts/n/a

agents

agents/n/a

assets

assets/n/a

Imported Reference Notes

Imported: Resources

• references/express-checkout.md: Express Checkout implementation guide
• references/ipn-handling.md: IPN verification and processing
• references/refund-workflows.md: Refund handling patterns
• references/billing-agreements.md: Recurring billing setup
• assets/paypal-client.py: Production PayPal client
• assets/ipn-processor.py: IPN webhook processor
• assets/recurring-billing.py: Subscription management

Imported: Express Checkout Implementation

Server-Side Order Creation

import requests
import json

class PayPalClient:
    def __init__(self, client_id, client_secret, mode='sandbox'):
        self.client_id = client_id
        self.client_secret = client_secret
        self.base_url = 'https://api-m.sandbox.paypal.com' if mode == 'sandbox' else 'https://api-m.paypal.com'
        self.access_token = self.get_access_token()

    def get_access_token(self):
        """Get OAuth access token."""
        url = f"{self.base_url}/v1/oauth2/token"
        headers = {"Accept": "application/json", "Accept-Language": "en_US"}

        response = requests.post(
            url,
            headers=headers,
            data={"grant_type": "client_credentials"},
            auth=(self.client_id, self.client_secret)
        )

        return response.json()['access_token']

    def create_order(self, amount, currency='USD'):
        """Create a PayPal order."""
        url = f"{self.base_url}/v2/checkout/orders"
        headers = {
            "Content-Type": "application/json",
            "Authorization": f"Bearer {self.access_token}"
        }

        payload = {
            "intent": "CAPTURE",
            "purchase_units": [{
                "amount": {
                    "currency_code": currency,
                    "value": str(amount)
                }
            }]
        }

        response = requests.post(url, headers=headers, json=payload)
        return response.json()

    def capture_order(self, order_id):
        """Capture payment for an order."""
        url = f"{self.base_url}/v2/checkout/orders/{order_id}/capture"
        headers = {
            "Content-Type": "application/json",
            "Authorization": f"Bearer {self.access_token}"
        }

        response = requests.post(url, headers=headers)
        return response.json()

    def get_order_details(self, order_id):
        """Get order details."""
        url = f"{self.base_url}/v2/checkout/orders/{order_id}"
        headers = {
            "Authorization": f"Bearer {self.access_token}"
        }

        response = requests.get(url, headers=headers)
        return response.json()

Imported: IPN (Instant Payment Notification) Handling

IPN Verification and Processing

from flask import Flask, request
import requests
from urllib.parse import parse_qs

app = Flask(__name__)

@app.route('/ipn', methods=['POST'])
def handle_ipn():
    """Handle PayPal IPN notifications."""
    # Get IPN message
    ipn_data = request.form.to_dict()

    # Verify IPN with PayPal
    if not verify_ipn(ipn_data):
        return 'IPN verification failed', 400

    # Process IPN based on transaction type
    payment_status = ipn_data.get('payment_status')
    txn_type = ipn_data.get('txn_type')

    if payment_status == 'Completed':
        handle_payment_completed(ipn_data)
    elif payment_status == 'Refunded':
        handle_refund(ipn_data)
    elif payment_status == 'Reversed':
        handle_chargeback(ipn_data)

    return 'IPN processed', 200

def verify_ipn(ipn_data):
    """Verify IPN message authenticity."""
    # Add 'cmd' parameter
    verify_data = ipn_data.copy()
    verify_data['cmd'] = '_notify-validate'

    # Send back to PayPal for verification
    paypal_url = 'https://ipnpb.sandbox.paypal.com/cgi-bin/webscr'  # or production URL

    response = requests.post(paypal_url, data=verify_data)

    return response.text == 'VERIFIED'

def handle_payment_completed(ipn_data):
    """Process completed payment."""
    txn_id = ipn_data.get('txn_id')
    payer_email = ipn_data.get('payer_email')
    mc_gross = ipn_data.get('mc_gross')
    item_name = ipn_data.get('item_name')

    # Check if already processed (prevent duplicates)
    if is_transaction_processed(txn_id):
        return

    # Update database
    # Send confirmation email
    # Fulfill order
    print(f"Payment completed: {txn_id}, Amount: ${mc_gross}")

def handle_refund(ipn_data):
    """Handle refund."""
    parent_txn_id = ipn_data.get('parent_txn_id')
    mc_gross = ipn_data.get('mc_gross')

    # Process refund in your system
    print(f"Refund processed: {parent_txn_id}, Amount: ${mc_gross}")

def handle_chargeback(ipn_data):
    """Handle payment reversal/chargeback."""
    txn_id = ipn_data.get('txn_id')
    reason_code = ipn_data.get('reason_code')

    # Handle chargeback
    print(f"Chargeback: {txn_id}, Reason: {reason_code}")

Imported: Subscription/Recurring Billing

Create Subscription Plan

def create_subscription_plan(name, amount, interval='MONTH'):
    """Create a subscription plan."""
    client = PayPalClient(CLIENT_ID, CLIENT_SECRET)

    url = f"{client.base_url}/v1/billing/plans"
    headers = {
        "Content-Type": "application/json",
        "Authorization": f"Bearer {client.access_token}"
    }

    payload = {
        "product_id": "PRODUCT_ID",  # Create product first
        "name": name,
        "billing_cycles": [{
            "frequency": {
                "interval_unit": interval,
                "interval_count": 1
            },
            "tenure_type": "REGULAR",
            "sequence": 1,
            "total_cycles": 0,  # Infinite
            "pricing_scheme": {
                "fixed_price": {
                    "value": str(amount),
                    "currency_code": "USD"
                }
            }
        }],
        "payment_preferences": {
            "auto_bill_outstanding": True,
            "setup_fee": {
                "value": "0",
                "currency_code": "USD"
            },
            "setup_fee_failure_action": "CONTINUE",
            "payment_failure_threshold": 3
        }
    }

    response = requests.post(url, headers=headers, json=payload)
    return response.json()

def create_subscription(plan_id, subscriber_email):
    """Create a subscription for a customer."""
    client = PayPalClient(CLIENT_ID, CLIENT_SECRET)

    url = f"{client.base_url}/v1/billing/subscriptions"
    headers = {
        "Content-Type": "application/json",
        "Authorization": f"Bearer {client.access_token}"
    }

    payload = {
        "plan_id": plan_id,
        "subscriber": {
            "email_address": subscriber_email
        },
        "application_context": {
            "return_url": "https://yourdomain.com/subscription/success",
            "cancel_url": "https://yourdomain.com/subscription/cancel"
        }
    }

    response = requests.post(url, headers=headers, json=payload)
    subscription = response.json()

    # Get approval URL
    for link in subscription.get('links', []):
        if link['rel'] == 'approve':
            return {
                'subscription_id': subscription['id'],
                'approval_url': link['href']
            }

Imported: Error Handling

class PayPalError(Exception):
    """Custom PayPal error."""
    pass

def handle_paypal_api_call(api_function):
    """Wrapper for PayPal API calls with error handling."""
    try:
        result = api_function()
        return result
    except requests.exceptions.RequestException as e:
        # Network error
        raise PayPalError(f"Network error: {str(e)}")
    except Exception as e:
        # Other errors
        raise PayPalError(f"PayPal API error: {str(e)}")

# Usage
try:
    order = handle_paypal_api_call(lambda: client.create_order(25.00))
except PayPalError as e:
    # Handle error appropriately
    log_error(e)

Imported: Testing

# Use sandbox credentials
SANDBOX_CLIENT_ID = "..."
SANDBOX_SECRET = "..."

# Test accounts
# Create test buyer and seller accounts at developer.paypal.com

def test_payment_flow():
    """Test complete payment flow."""
    client = PayPalClient(SANDBOX_CLIENT_ID, SANDBOX_SECRET, mode='sandbox')

    # Create order
    order = client.create_order(10.00)
    assert 'id' in order

    # Get approval URL
    approval_url = next((link['href'] for link in order['links'] if link['rel'] == 'approve'), None)
    assert approval_url is not None

    # After approval (manual step with test account)
    # Capture order
    # captured = client.capture_order(order['id'])
    # assert captured['status'] == 'COMPLETED'

Imported: Common Pitfalls

• Not Verifying IPN: Accepting IPN without verification
• Duplicate Processing: Not checking for duplicate transactions
• Wrong Environment: Mixing sandbox and production URLs/credentials
• Missing Webhooks: Not handling all payment states
• Hardcoded Values: Not making configurable for different environments

Imported: Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.