Protecting user addition to DB


I am using auth0 for user authentication and authorization but, I want that after each new signup a new user will be added to the data base.
I want protect the user addition though so only a user with a specific jwt claim will be able to create other users.
Is it possible and if yes how.
I thought about a rule in auth0 that happens only on signup but than I still need to create a jwt with a claim admin somehow.

I need help with that