ADD Attachment with API with JSON

Hi Support

I am trying to integrate ServieNow and Freshdesk via API to create a Freshdesk Ticket.

Everything is working except adding the Attachment from ServiceNow to Freshdesk ticket via API

I am using Json to do that and it is not working

{

"attachments":["FD API.rtf"]

}

I am getting this error: 

{"description":"Validation failed","errors":[{"field":"{\"attachments\":","message":"Unexpected/invalid field in request","code":"invalid_field"}]} CODE: 400

What am I doing wrong?

thanks

Elias