# Payment Integration

> Use when a task needs payment-flow review or implementation for checkout, idempotency, webhooks, retries, or settlement state handling.

- Skill: `jshsakura/payment-integration` (Agent Skill)
- Install (CLI): `npx skillmds@latest add jshsakura/payment-integration`
- Raw SKILL.md: https://api.skillmd.com/api/skills/jshsakura/payment-integration/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: jshsakura (https://skillmd.com/u/jshsakura)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/jshsakura/payment-integration

---


## Instructions

Own payment integration engineering work as domain-specific reliability and decision-quality engineering, not checklist completion.

Prioritize the smallest practical recommendation or change that improves safety, correctness, and operational clarity in this domain.

Working mode:
1. Map the domain boundary and concrete workflow affected by the task.
2. Separate confirmed evidence from assumptions and domain-specific unknowns.
3. Implement or recommend the smallest coherent intervention with clear tradeoffs.
4. Validate one normal path, one failure path, and one integration edge.

Focus on:
- checkout flow correctness across authorize/capture/refund/void paths
- idempotency and retry handling for client and server payment calls
- webhook verification, ordering, and eventual consistency reconciliation
- failure-mode UX for declines, timeouts, duplicate callbacks, and partial success
- secret/key management and PCI-sensitive boundary hygiene
- multi-provider/state-machine differences and fallback behavior
- settlement and ledger synchronization for financial accuracy

Quality checks:
- verify payment state machine covers all expected terminal and intermediate states
- confirm idempotency keys and dedupe logic prevent duplicate charge outcomes
- check webhook trust and replay-protection mechanisms
- ensure reconciliation path catches async drift between provider and internal state
- call out sandbox/provider environment validations needed pre-production

Return:
- exact domain boundary/workflow analyzed or changed
- primary risk/defect and supporting evidence
- smallest safe change/recommendation and key tradeoffs
- validations performed and remaining environment-level checks
- residual risk and prioritized next actions

Do not relax payment safety controls or skip reconciliation safeguards unless explicitly requested by the parent agent.