How to add modifiers to cart line item in BigCommerce Api - api

Question

I already tried the solution given in this Cart API V3: Can't create a Cart for product that has options link but it's not working for me.
modifier is extra fitting added to the product like "name tag" for suitcase.
I tried to add the modifier in "option_selections" like below but it returns 422 error.
Request:
{
"quantity":"1",
"product_id":"5846",
"variant_id":150922,
"list_price":" 170.00",
"option_selections":[{"option_id":23800, "option_value":"10088"}]
}
Response:
StatusCode: 422, ReasonPhrase: 'Unprocessable Entity'
Thanks for your reply in advance.

Answer 1

If you're creating a new cart, try this request body (POST to /carts endpoint):
{
"line_items": [
{
"quantity": 1,
"product_id": 76,
"list_price": 170.00,
"option_selections": [
{
"option_id": 21506,
"option_value": 10090
}
]
}
]
}
You shouldn't have quotes around any of these field values--list_price, product_id, etc all accept a number, not a string.
If you want to add a new line item to an existing cart, you can use the same request body as above. The request will be a POST to carts/{cartID}/items
EDIT:
If you are updating a line item that already exists in the cart, you'll want to make a PUT to /carts/{cartID}/items/{itemID}.
Request body:
{
"line_item": {
"quantity": 1,
"product_id": 76,
"list_price": 170.00,
"option_selections": [
{
"option_id": 21506,
"option_value": 10090
}
]
}
}
Note: it does need to be "line_item" rather than "line_items" when updating a single cart item. I'll work with our documentation team to get this updated in the API reference.

Answer 2

I was able to solve the issue, though I agree with Karen White's answer, I wanted to add a product which has options like colors and modifiers too. Which I was not able to achieve with that. I used the following data to add product with option and modifier.
Instead of passing variant_id, pass variant as option (option_id gets option's id and option_value gets option value's id) and pass modifier as option (modifier option_id gets option's id and option_value gets option value's id)
{
"line_items": [{
"quantity": 1,
"product_id": 5846,
"option_selections": [{
"option_id": 23799,
"option_value": 10173
}, {
"option_id": 23800,
"option_value": 10088
}]
}]
}