# Get one-time add-ons for a membership contract

Retrieves all one-time product additions scheduled for upcoming orders of a specific membership contract. One-offs are products added to a single billing cycle without affecting the recurring subscription items.

Key Information Returned:
- One-Off Items: List of products added to upcoming orders
- Product Details: Variant ID, handle, title, price, image
- Billing Association: Which billing attempt the item is added to
- Quantity: Number of units for the one-time add-on
- Status: Active, pending, or fulfilled one-offs
- Created Date: When the one-off was added

One-Off Item Data:
- Contract ID: Parent subscription contract
- Billing Attempt ID: Specific order the item will be added to
- Variant Info: Product variant being added
- Pricing: One-time price for the add-on
- Fulfillment Status: Whether item has been shipped

Use Cases:
- Display scheduled one-time add-ons in customer portal
- Show customers which extra items are in next order
- Sync one-off data with external order management systems
- Generate custom order previews for customers
- Build upsell dashboards showing add-on purchases
- Track one-time product revenue per contract

Authentication: Requires API key authentication via X-API-Key header or api_key parameter

Endpoint: GET /api/external/v2/subscription-contract-one-offs-by-contractId
Version: 0.0.1

## Query parameters:

  - `api_key` (string)
    API Key (Deprecated - Use Header X-API-Key instead)

  - `contractId` (integer, required)
    Subscription contract ID
    Example: 123456

## Header parameters:

  - `X-API-Key` (string)

## Response 200 fields (application/json):

  - `id` (integer)

  - `shop` (string, required)

  - `billingAttemptId` (integer)

  - `subscriptionContractId` (integer)

  - `variantId` (integer)

  - `variantHandle` (string)

## Response 401 fields (*/*):

  - `id` (integer)

  - `shop` (string, required)

  - `billingAttemptId` (integer)

  - `subscriptionContractId` (integer)

  - `variantId` (integer)

  - `variantHandle` (string)

## Response 403 fields (*/*):

  - `id` (integer)

  - `shop` (string, required)

  - `billingAttemptId` (integer)

  - `subscriptionContractId` (integer)

  - `variantId` (integer)

  - `variantHandle` (string)

## Response 404 fields (*/*):

  - `id` (integer)

  - `shop` (string, required)

  - `billingAttemptId` (integer)

  - `subscriptionContractId` (integer)

  - `variantId` (integer)

  - `variantHandle` (string)