How to identify system field and custom fields in custom-fields api?

When I list deal custom fields, API returns records much more than I added custom fields。
Is there an attribute from response data to identify from system default fields to use custom fields?
Thanks for the answers.

Hey @newpepsichina
Welcome to the community :wave:
From this, I understand that you are seeing a lot more custom fields than you could see in the web app / created by yourself?

You can identify a custom field through the edit_flag. If it’s true then it’s a custom field, if it’s false it is a default field (non-custom field)

*Edit 1: Corrected the field name