Setting a lambda function on custom attribute using API

Hi all,

This might be a basic question but I couldn’t figure it out or find it on the documentation.

Is it possible to set up a lambda function on a custom attribute as I would do in the file configuration:

“vars.os” : “{{ Math.random() * 100 }}”

But it sets the variable as a string.

otherwise it is not a valid json.

I have tried multiple variations but none of them have worked. Is there any way to make it work?

Thanks in advance.