What is the best way to troubleshoot inserting a contact via api?

What is the best way to troubleshoot inserting a contact via api?

Hi,

Is there a log file or something I can view.
I am trying to use a third party system that we have already invested in that also works with other companies api's.

only difference with Zoho api is that there is this concept of entity name (contacts) & row numbers.
Thanks in advance
todd