You can use this code for a GET call from the cluster API Docs and look at the response field "state" to see the status. You will want to swap out the domain for your workspace's domain and the cluster ID of the cluster you are monitoring.

curl --netrc -X GET \
https://<DOMAIN>.cloud.databricks.com/api/2.0/clusters/get \
--data '{ "cluster_id": "1<CLUSTER ID>" }' \
| jq .

Hope this helps!