At the moment the writers are taken from the credits tag. They have to be marked with the keyword writer in parantheses. e.g. <credits>Emily Wachetel (Guest Star) / Nancy Wetzel (Guest Star) / J.J. Abrams (Writer)</credits> Based on the nfo of your Helix tvshow, you have multiple credits tags and those are all without the keyword.
Looking at the xmbc nfo wiki, credits are assumed to be writers if without keyword. So the agent will have to be changed to accept that.