For AI agents: llms.txt is a short guide that sends you to the rules your problem needs, and rules.json holds every rule of this playbook as JSON.

Applies when

The project it takes payments.

How to do it

A card number on your server puts the whole system under the full PCI DSS assessment. A leak of stored cards ends most small businesses. The payment provider's hosted page or fields keep the number on its servers and give you a token. Saved cards then live with the provider, which can move them to another provider when you leave. Build the checkout as Choose a checkout that keeps you on SAQ A says.

Examples

Using these examples: they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

JavaScript example

const CARD_FIELDS = /\b(card_?number|cvc|cvv|pan)\b/i;

export const cardFieldsIn = (body) => Object.keys(body).filter((field) => CARD_FIELDS.test(field));

Python example

import re

CARD_FIELDS = re.compile(r"\b(card_?number|cvc|cvv|pan)\b", re.IGNORECASE)

def card_fields_in(body: dict) -> list[str]:
    return [field for field in body if CARD_FIELDS.search(field)]

Related rules

• Choose a checkout that keeps you on SAQ A in Payments