Omeka PHP API Post request


I am using Omeka Classic REST API with the ZendService_Omeka for PHP to perform a POST request. The idea is to create a new Annotation Item for an existing image item. I was able to make the Configuration, to perform GET requests, etc… but when I try to make a POST request, I keep receiving the message “POST requests must not include an ID.”, even though the POST request only holds a JSON string and all Ids have been removed from it.

Does anyone knows the exact reason for the message?