Adding a single item through Zoho Books API returns {"code":4,"message":"Invalid value passed for bulk_update"}

Hello,

I need to update an invoice with hidden items (rate = 0) in order to have the inventory updated accordingly, as well as monitoring the full project's economical efficiency.

To do so, I am passing the Zoho CRM customer ID, Project Name, Article ID and name to a function. From there I can find the latest invoice linked to our customer and project.

I then try to update the invoice by adding a single line item with quantity = 1 and rate = 0 but get a code = 4 response :(

Here is the part where I try to update the invoice:

if(found_invoice = true)
{
//Found invoice: add item on invoice.
//1. get access_token to use api
access_token = thisapp.getAccessTokenFromRefreshToken();
authorization_string = "Zoho-oauthtoken " + access_token;
//2. List invoices from customer:
parameters_data = {"customer_id":customer_id,"invoice_number":invoice_number,"line_items":[{"item_id":article_id,"name":article,"description":article,"quantity":"1.00","rate":0}]};
headers_data = Map();
headers_data.put("Authorization",authorization_string);
response = invokeurl
[
url :"https://www.zohoapis.eu/books/v3/invoices?organization_id=XXXXXXXXXXX"
type :PUT
parameters:parameters_data.toString()
headers:headers_data
connection:<connection>
content-type:"application/json"
];
info response;
}