Create a rule on a promotion

import { createAdminClient } from '@spree/admin-sdk'

const client = createAdminClient({
  baseUrl: 'https://your-store.com',
  secretKey: 'sk_xxx',
})

const rule = await client.promotions.rules.create('promo_UkLWZg9DAJ', {
  type: 'currency',
  preferences: { currency: 'EUR' },
})

{
  "id": "prorule_UkLWZg9DAJ",
  "created_at": "2026-06-17T13:37:48.759Z",
  "updated_at": "2026-06-17T13:37:48.759Z",
  "type": "currency",
  "promotion_id": "promo_UkLWZg9DAJ",
  "preferences": {
    "currency": "EUR"
  },
  "preference_schema": [
    {
      "key": "currency",
      "type": "string",
      "default": null
    }
  ],
  "label": "Currency",
  "product_ids": null,
  "category_ids": null,
  "customer_ids": null
}