Clarification on status and user_data Fields in Create an Agent API

Dear D-ID Support Team,

I am currently reviewing the Create an Agent API documentation, but I could not find detailed descriptions for the following fields:

user_data (string, length 1–1000): What is the purpose of this field, and how should it be used?
Additionally, I would like to know if custom knowledge can be used with this API. If so, could you provide guidance on how to integrate it?

I would appreciate your clarification on these points.

Best regards