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

Without a pinned version, requests and webhook events follow the account's default version, which someone can change in the dashboard. Stripe, for example, ships a new version every month and breaking changes twice a year. Many SDKs pin the version they were built for, so an SDK upgrade is an API upgrade. Create each webhook endpoint with the same version as the SDK. To upgrade, run the payment tests against the new version in test mode first. Update the SDK as Update dependencies in small automatic steps describes.

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 PAYMENT_API_VERSION = '2026-09-30.endive'
const stripe = new Stripe(process.env.PAYMENT_API_KEY, { apiVersion: PAYMENT_API_VERSION })

await stripe.webhookEndpoints.create({
  url: 'https://example.com/webhooks/payments',
  enabled_events: ['payment_intent.succeeded', 'charge.refunded'],
  api_version: PAYMENT_API_VERSION,
})

Python example

PAYMENT_API_VERSION = "2026-09-30.endive"
stripe.api_version = PAYMENT_API_VERSION

stripe.WebhookEndpoint.create(
    url="https://example.com/webhooks/payments",
    enabled_events=["payment_intent.succeeded", "charge.refunded"],
    api_version=PAYMENT_API_VERSION,
)

How to check

The code sets the API version in one constant, and the provider's webhook endpoint list shows that same version. A test fails when the SDK reports a different version than the constant.

Sources

• Stripe API versioning

Related rules

• Update dependencies in small automatic steps in Engineering
• Use Stripe for payments in Software choices