Do you see a chance to get the Host Custom Attributes of each esxi hosts in vRealize Operation Manager using REST API?
What does "vRealize" mean? vRealize is a suite of products that includes offerings like vRealize Automation, vRealize Log Insight, and vRealize Operations Manager. You have posted in the vRealize Automation sub-forum, but which do you mean?
You have edited your post to say "vRealize Operations Manager" which puts this question in the wrong sub-forum. Please move to vRealize Operations.