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.
npx skills add petrkindlmann/qa-skills --skill payment-testinggit clone --depth 1 https://github.com/petrkindlmann/qa-skillsWrote 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.
[](https://agentmods.dev/skills/petrkindlmann/qa-skills/payment-testing)<a href="https://agentmods.dev/skills/petrkindlmann/qa-skills/payment-testing"><img src="https://agentmods.dev/badge/skills/petrkindlmann/qa-skills/payment-testing/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/petrkindlmann/qa-skills/payment-testing"><img src="https://agentmods.dev/badge/skills/petrkindlmann/qa-skills/payment-testing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk warn
- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00192 | $0.05173 |
| Opus 5.5 | $0.00077 | $0.02069 |
| Sonnet 5.5 | $0.00038 | $0.01035 |
| Haiku 4.5 | $0.00019 | $0.00517 |
Grade A, and why
payment-testing 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 yesterday.
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.
How it starts
The opening of the file, as written. The whole thing — 389 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Quick Route
| You need to test… | Go to | Reference |
|---|---|---|
| Success / decline / insufficient-funds outcomes | Test cards | references/stripe-test-cards.md |
| A 3DS/SCA challenge that pops a modal | 3DS challenge | references/playwright-3ds.md |
| A subscription renewal months/years out | Test clocks | references/webhooks-and-clocks.md |
| Webhooks reaching localhost + signatures | Webhooks | references/webhooks-and-clocks.md |
| A non-Stripe or in-house webhook protocol | Webhooks, "Another provider" | the provider's or your contract's docs |
| A failed renewal then a refund | Failed payments | references/webhooks-and-clocks.md |
| Fulfillment only after real payment | Reconciliation | references/webhooks-and-clocks.md |
| Adyen / PayPal / Braintree sandboxes | Multi-PSP | references/multi-psp.md |
Discovery Questions
First, check .agents/qa-project-context.md in the project root and skip anything it
already answers (PSP, stack, test framework, existing fixtures). Then clarify:
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- yesterday Changed · +12 lines ab76ecc58d16
- 3d ago Changed · +4 lines d2e4b9b7f5aa
- 1mo ago First seen · 373 lines · 192 tokens per session scan A 36dada06d6d0
payment-testing is a skill published in the GitHub repository petrkindlmann/qa-skills (207 stars, last pushed 2d ago), licensed MIT. It adds 192 tokens to every session and 5,173 once invoked, about $0.0008 per session on Opus 5.5. 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 2026-08-30.
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