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 sumup/sumup-skills --skill sumup-best-practicesgit clone --depth 1 https://github.com/sumup/sumup-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/sumup/sumup-skills/sumup-best-practices)<a href="https://agentmods.dev/skills/sumup/sumup-skills/sumup-best-practices"><img src="https://agentmods.dev/badge/skills/sumup/sumup-skills/sumup-best-practices/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/sumup/sumup-skills/sumup-best-practices"><img src="https://agentmods.dev/badge/skills/sumup/sumup-skills/sumup-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00062 | $0.00704 |
| Opus 5.5 | $0.00025 | $0.00282 |
| Sonnet 5.5 | $0.00012 | $0.00141 |
| Haiku 4.5 | $0.00006 | $0.00070 |
Grade A, and why
sumup-best-practices 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 76 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SumUp Integration Decisions and Best Practices
Knowledge and APIs can change. Always prefer the latest SumUp docs in markdown format over stale memory.
- Docs root:
https://developer.sumup.com/ - LLM entrypoint:
https://developer.sumup.com/llms.txt
Use this skill for architecture and security decisions, not implementation walkthroughs.
Quick Decision Tree
Need to accept a payment?
├─ In-person (card-present)
│ ├─ Native mobile app controls reader directly -> iOS Terminal SDK / Android Reader SDK
│ ├─ POS/backend controls Solo from non-native environment -> Cloud API
│ └─ Legacy handoff to SumUp app is mandatory -> Payment Switch
└─ Online (card-not-present)
├─ Fastest redirect flow, no embed required -> Hosted Checkout
├─ Embedded payment form with low PCI scope -> Card Widget
├─ Mobile app checkout UX -> Swift Checkout SDK / React Native SDK
├─ Save card and charge later -> Customers + tokenization
└─ Custom orchestration needs -> Checkouts API + 3DS + webhooks
Start Here
- Classify the request:
terminal,online, orhybrid. - Choose the lowest-complexity viable path first:
- Prefer Hosted Checkout or Card Widget before custom orchestration.
- Prefer Cloud API for non-native Solo control.
- Select auth model:
- API key for single-merchant server integrations.
- OAuth 2.0 for delegated or multi-merchant apps.
- Confirm restricted access and affiliate prerequisites:
paymentsscope activation where needed.- Affiliate Key plus app/bundle identifier alignment for card-present.
- Confirm operational constraints:
- Currency/merchant alignment
- Webhook endpoint readiness and idempotency
- Legacy compatibility requirements
Non-Negotiable Rules
- Keep API keys and OAuth secrets server-side only.
- Never handle raw PAN/card details directly.
- Create online checkouts server-to-server.
- Prefer hosted/widget/SDK checkout UI over custom card handling.
- Avoid deprecated endpoints.
- Use unique transaction references (
checkout_reference,foreignTransactionId, or equivalent). - Treat webhook callbacks as signals and verify final state via API before fulfillment.
- Assume retries and duplicate deliveries; enforce idempotent backend handling.
What ships with it
3 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.
- 1mo ago First seen · 76 lines · 62 tokens per session scan A 1d210ff2a82a
sumup-best-practices is a skill published in the GitHub repository sumup/sumup-skills (5 stars, last pushed yesterday), licensed Apache-2.0. It adds 62 tokens to every session and 704 once invoked, about $0.0002 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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