You can see the status information when you GET the documents; I think that way, you can confirm if the contracts have been signed or not.
When you GET with this API, the response contains a status parameter, and in the case of status 2, it's a status that indicates that both parties have signed.
Also, the best timing to throw this API is, for example, is in record details.
Here is a CloudSign Web API on SwaggerHub:
Document Status :
* 0 - Drafts
* 1 - Currently Confirming
* 2 - Completed
* 3 - Cancellation or Rejection
* 4 - Templates
* 13 - Imported Documents
Hopefully, this helps.