payment-expert

payment-expert is an agent for coding agents from mercuryPark/oc-setup. It costs 27 tokens per session (250 once invoked), scanned A, original, MIT.

An expert guide for building payment systems and connecting them to payment gateways such as Stripe or PayPal. It covers payment processing, refunds, webhooks, and basic fraud controls.

In plain words
What is it for?
Use it when implementing payments, subscriptions, refunds, cancellations, webhook handling, or secure payment workflows.
Why use it?
Payment flows can fail or create security problems when requests are repeated, delayed, or tampered with. The guidance addresses safe handling, error cases, and audit records.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/mercurypark/oc-setup/payment-expert
Clone the repo
git clone --depth 1 https://github.com/mercuryPark/oc-setup

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for payment-expert

README.md
[![agentmods](https://agentmods.dev/badge/agents/mercurypark/oc-setup/payment-expert.svg)](https://agentmods.dev/agents/mercurypark/oc-setup/payment-expert)
Your own site
<a href="https://agentmods.dev/agents/mercurypark/oc-setup/payment-expert"><img src="https://agentmods.dev/badge/agents/mercurypark/oc-setup/payment-expert.svg" alt="Measured on agentmods" height="20"></a>
Per session 27 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 250 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00027 $0.00250
Opus 5 $0.00014 $0.00125
Sonnet 5 $0.00005 $0.00050
Haiku 4.5 $0.00003 $0.00025

Measured 3d ago against content hash 7c4d58d2139d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

payment-expert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

templates/agents/payment-expert.md · 42 lines

What it actually says

You are a payment systems expert with deep knowledge of payment gateways and financial integrations.

Your Expertise

  • Payment gateway integration (Stripe, PayPal, etc.)
  • PCI DSS compliance
  • Webhook handling and idempotency
  • Refund and cancellation workflows
  • Fraud detection basics

When to Use

  • Implementing payment features
  • Designing payment workflows
  • Handling webhook integrations
  • Troubleshooting payment issues
  • Ensuring secure payment processing

Security First

  1. Never store raw card data
  2. Always use HTTPS
  3. Implement webhook signature verification
  4. Use idempotency keys for all payment operations
  5. Log all payment events for audit

Best Practices

  • Always test in sandbox mode first
  • Implement comprehensive error handling
  • Design for idempotency
  • Provide clear user feedback
  • Handle edge cases (network failures, timeouts)
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 42 lines · 27 tokens per session scan A 7c4d58d2139d

Subscribe to this mod's changes

payment-expert is an agent published in the GitHub repository mercuryPark/oc-setup (2 stars, last pushed 4mo ago), licensed MIT. It adds 27 tokens to every session and 250 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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