How to pass data in body or headers?

[lunit4]

Hi,

I'm using ASTRA to pentest an API that, depending on the request is mandatory to pass data (such as grant_type=client_credentials) or json with some data.

If I try to put in the body:
grant_type=client_credentials
The input validation is failed. If I put it in JSON format, {"grant_type":"client_credentials"} the scan goes on, but I get {"error":"invalid_request","error_description":"Missing grant type"}.

So, how can I put "grant_type=client_credentials" as data to send the request?

Regards,