Hi @Udesh Chathuranga Sendanayake ,
I wrote a quickstart blog post about SCOM REST API, I suggest you have a look at my examples there:
https://thesystemcenterblog.com/2020/07/09/quick-start-scom-rest-api/
My examples use PowerShell which is a modern but also a great way if you want to start automating.
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Best regards,
Leon