Loop happens when trying to add string to a filename via AppleScript

Question

I am trying to write an AppleScript that can add the current time to a folder's name.

on adding folder items to this_folder after receiving these_items
    repeat with this_item in these_items
        tell application "Finder"
            set t to (time string of (current date))
            set name of this_item to (t & " " & (name of this_item))
        end tell
    end repeat
end adding folder items to

I have added the script as a Folder Action for a specific folder so it will automatically rename every folder that is being put into it. But when I add a folder to the one with the script as a Folder Action the time is being added repeatedly until the folder's name is too long to add more characters to it. How can I make it so the time is only being added once?

Thank you in advance!