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

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

const action = await client.promotions.actions.create('promo_UkLWZg9DAJ', {
  type: 'free_shipping',
})

spree api post /promotions/{promotion_id}/promotion_actions -d '{"type":"free_shipping"}'

{
  "id": "pact_UkLWZg9DAJ",
  "created_at": "2026-01-15T12:00:00.000Z",
  "updated_at": "2026-01-15T12:00:00.000Z",
  "type": "free_shipping",
  "promotion_id": "promo_UkLWZg9DAJ",
  "preferences": {},
  "calculator": null,
  "line_items": null
}

{
  "error": {
    "code": "unknown_promotion_action_type",
    "message": "Unknown type"
  }
}