# Bulk add products or variants to an existing subscription group

Adds multiple products and/or product variants to an existing subscription group (selling plan group) using a JSON request body. This endpoint is ideal for adding large numbers of products/variants that would exceed URL length limits in the query parameter version.

Advantages over query parameter endpoint:
- No URL length restrictions
- Cleaner syntax for large lists
- Better for programmatic integrations
- Supports the same functionality with improved scalability

Behavior:
- Identical to the query parameter endpoint in functionality
- Adds products/variants to existing assignments
- Preserves product order
- Updates synchronously and returns the updated group

Authentication: Requires valid X-API-Key header

Endpoint: POST /api/external/v2/subscription-groups/{id}/bulk-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"

## Query parameters:

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

## Request fields (application/json):

  - `productIds` (array)

  - `variantIds` (array)