Stop Service Manager web service execution

Hello experts

I need to validate the CI and other fields send via web service to create an IM record.

I did some test and I received the response of the web service with a message that says the CI is invalid but the incident record is created

How do I need to do to stop web service execution when the CI is invalid? Exist a validation to stop the action executed?

Could you have some idea to do this?

Thanks in advance

Best regards