How to insert a label_entry via REST API?

Hi all,

I tried to create a label_entry via REST API, the label_entry is created but the field table_key is empty.

/api/now/table/label_entry {"label":"630086900f23320050c8cfdce1050efc","table":"incident","table_key":"7e1146100f23320050c8cfdce1050e5f","title":"Incident - INC0020001"}

Any idea why table_key   is not added?