If your third party tools have an API, you can still use "Call HTTP Web Service" or "Web Request" action in your workflow to use the API of your tools. But be carefull if your third party tools need authentication. 

You can use Nintex Xtension : 

https://www.nintex.com/blog/know-easily-adapt-extend-workflows-nintex-xtensions/

https://help.nintex.com/sdk/Content/SDKHome.htm

Otherwise you can do it with just workflow logic. For example, you can store your "rules" (like expected value, result ...) in a SharePoint list, query this list, and interpret your result.