How do I set insight custom field value through Jira API on Jira software/datacenter?

[John Abraham]

 'project': {'key': 'JIRA'},
'summary': "test summary",
'description': "test description",
'reporter': {'name': "admin"},
'issuetype': {'name': "Task"},
"customfield_18200": [{"key" : "SERVICE-4659"}]

I keep getting 

response text = {"issues":[],"errors":[{"status":400,"elementErrors":{"errorMessages":[],"errors":{"customfield_18200":"Field 'customfield_18200' cannot be set. It is not on the appropriate screen, or unknown."}},"failedElementNumber":0}]}