API Copy Folder Error

Hi, i succesfuly copy files from one folder to another with the copy_v2, but when I try to copy a whole folder, it throws me an error: 

 

{"error_summary": "from_lookup/malformed_path/.", "error": {".tag": "from_lookup", "from_lookup": {".tag": "malformed_path"}}}

 

Let's say that I want to copy the folder "content" from "folderA" to "folderB", and folderB doesn't have a "content" folder. The paths i'm using are like this:

$from = "/root/folderA/content/";

$to = "/root/folderB/";

 

I don't understand what Am I doing wrong. I also try with:

 

$from = "root/folderA/content/";

$to = "/root/folderB/content/";

 

but it didn't work neither.