Payments Integration Expert

Generic AI gives you the payments quickstart. This Agent gives you what the quickstart leaves out, the failure modes that cost real money in production. Built by a developer who ships production card-present and e-commerce payment integrations, it responds like a senior payments engineer reviewing your work, not a docs summary.

What it does

• Code review, red-flag first. Paste any payment-related code and it runs a 10-point severity scan for the bugs that lose money: client-supplied amounts, fulfillment on redirect instead of webhook, missing idempotency keys, unverified webhook signatures, floating-point money, missing terminal-state checks, secrets in client code, and more.
• Provider selection. A structured framework across Stripe, Adyen, Braintree, PayPal and regional PSPs - by volume, geography, business model, engineering appetite, and risk. Includes fee literacy (blended vs interchange-plus) and why authorization rate beats fee rate at scale.
• Architecture guidance. The canonical payment flow, an explicit order state machine, auth-vs-capture, money representation, and multi-currency handling.
• SCA / 3DS / PSD2. Exemption strategy, and the MIT vs CIT distinction that silently breaks EU subscription renewals.
• Webhooks & idempotency. Reliable handlers under at-least-once, out-of-order delivery; deduplication, race conditions, and reconciliation.
• Subscriptions & billing. Dunning, smart retries, involuntary-churn recovery, proration, and bank-debit mandates.
• Disputes, refunds & fraud. Chargeback deadlines, evidence by reason code, the dispute-ratio thresholds that can get you blacklisted, and fraud prevention that doesn't kill conversion.
• PCI & go-live. Scope minimization, tokenization strategy, and a full pre-launch test matrix and checklist.

Who it's for

Developers, tech leads, and founders integrating or hardening a payment system - whether you're picking a provider, debugging a live webhook issue, or asking "did I miss anything before launch?"

How to use it

• Review my code: paste the handler, checkout, or charge logic.
• Which provider: describe your volume, markets, and business model.
• Debug: describe the symptom (e.g. "EU renewals failing with authentication_required").
• Pre-launch: ask for the go-live checklist for your setup.

Example prompts

• "Review this Stripe webhook handler for reliability issues."
• "We do ~$80k/month, US + Germany. Stripe or Adyen?"
• "Our EU subscription renewals started failing with 'authentication required' — why?"
• "Walk me through a go-live checklist for a marketplace on Stripe Connect."

Scope & limitations

Engineering guidance, not legal or compliance certification. PCI, PSD2, and tax outcomes depend on your jurisdiction and business specifics - it will flag when you need a QSA, lawyer, or accountant. It verifies current provider API details against official docs rather than guessing.