Cart Transformation API not accepting Valid product ID in expanded cart items

Technical Q&A
1

Am trying to make a cart transform function which will add a product as gift with particular items

when i return the functionRunResult with expandedCartItems. i added the id of the product to the merchandiseId field.

but the function keeps throwing the error even though the ID is of a valid Product

"operations[0] (expand): \[{code: invalid_component_merchandise_id, message: One or more of the expanded cart items have an invalid merchandise id.}\]"

this is the whole input/output/error log

{
  "shopId": 

Any help is much appreciated.
Thanks
2

After sending it thought inputs as a metafield attached to the product i was able to use the product ID in the expand operation