I know that every command that I enter in Kubernetes communicate with API.
Now I want to speak to API directly. How can I find json format for every command?
I suggest using a client library if you talk from a programming language:
https://kubernetes.io/docs/reference/#api-client-libraries
Or use kubectl
if you talk from CLI. Hardcoding API schemas will add you a maintenance burden. You're basically reimplementing the client in this case.
Following is the kubernetes API reference docs, you can find equivalent API for each resources here:
https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.13/
Hope this helps