Custom variables for job api

I am using rest API to run manual jobs in GitLab CI. When i start a manual job from UI I am able to define custom variables that i can use during the job. How can i define them when running job through API?

Could not find any documentation on it. Or not even a single question in forums.

This is how i currently run my job

curl -k --request POST --header “PRIVATE-TOKEN: abc”

I tried adding:

–form variables[TEST]=hello

But this didnt work.