I see the SNS option is available only in the UI and CLI/API, I guess the UI/CLI creates Cloudwatch Events rule for you in the background, you create your own rule using AWS::Events::Rule
Reference: Event Patterns
EventRule: Type:
"AWS::Events::Rule"
Properties: Description:
"EventRule"
EventPattern:
source: - "aws.inspector"
detail-type: - "AWS API Call via CloudTrail"
resources: - arn:aws:inspector:us-west-2:123456789012:target/0-nvgVhaxX/template/0-7sbz2Kz0 detail:
eventSource: - "inspector.amazonaws.com"
eventName: - "ASSESSMENT_RUN_COMPLETED"
State: "ENABLED"
Targets: - arn:aws:sns:us-west-2:123456789012:exampletopic