# Add products or variants to an existing subscription group

Adds one or more products and/or product variants to an existing subscription group (selling plan group). This endpoint provides a simple way to expand the product catalog eligible for subscription without modifying the group's configuration or existing product assignments.

Key Features:
- Add multiple products and variants in a single request
- Preserves existing product and variant assignments
- Maintains the order of products as provided
- Updates delivery profiles automatically if needed
- Synchronously updates Shopify and returns the updated group
- Optional response enhancement with added products information

Important Notes:
- Product IDs should be numeric Shopify product IDs without the gid:// prefix
- Variant IDs should be numeric Shopify variant IDs without the gid:// prefix
- Adding products also makes all their variants eligible for subscription
- Adding specific variants limits subscription eligibility to those variants only
- Duplicate products/variants are handled gracefully by Shopify
- URL length limits apply to the comma-separated lists (use bulk endpoint for large additions)
- Include 'x-return-short-response: true' header to get only added products/variants information in response

Use Cases:
- Launch new products with subscription options
- Add seasonal items to existing subscription groups
- Enable subscription for specific product variants
- Expand subscription eligibility without changing plan configurations
- Track which products were added in the current request

Authentication: Requires valid X-API-Key header

Endpoint: PUT /api/external/v2/subscription-groups/{id}/add-products
Version: 0.0.1

## Path parameters:

  - `id` (integer, required)
    Subscription group ID (numeric ID)
    Example: 123456789

## Header parameters:

  - `X-API-Key` (string, required)
    API Key for authentication
    Example: "sk_live_1234567890abcdef"

  - `x-return-short-response` (boolean)
    Header to indicate if response should return only added products ID information. Set to 'true' for minimal response, any other value or omitted for full response.

## Query parameters:

  - `productIds` (string)
    Comma-separated list of Shopify product IDs to add. Adding a product makes all its variants eligible for subscription. Use numeric IDs only (e.g., '987654321,987654322,987654323')
    Example: "987654321,987654322,987654323"

  - `variantIds` (string)
    Comma-separated list of Shopify variant IDs to add. Use this to enable subscription for specific variants only. Use numeric IDs only (e.g., '123456789,123456790,123456791')
    Example: "123456789,123456790"

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


## Response 400 fields

## Response 401 fields

## Response 404 fields

## Response 422 fields