You should give the agents permissions in Five9 admin to allow them to update contact records, then instead of using a script - add contact variables in five9 admin under contact and fields, then add those variables to a campaign using the campaign profiles under the layout tab and make sure that the read only box is unchecked. Then, when an agent gets a call, they will be able to write to those variable fields which they will be able to find in the interaction tab on their five9 agent desktop, and when the agent dispositions the call, the contact record will be updated with their input from the variable fields