How to pass var body params to http webhook

Hi, I need to pass var params into http put webhook body.
My content-type is application/json
My custom body is:
{ "id":{{group_id}}, "newName":{{novo_nome_grupo}} }
where 'group_id' is a var: 120363146612174483@g.us
and 'novo_nome_grupo' is a var: test.

I am getting the next error on my back:
24/01/2024 10:52:16 Unexpected token @ in JSON at position 24 - SyntaxError: Unexpected token @ in JSON at position 24 at JSON.parse (<anonymous>) at parse (F:\Programas\vuejs\izing.open.io\backend\node_modules\body-parser\lib\types\json.js:89:19)

What am I doing wrong?