VirusTotal’ Terms of Service specify the way you could use their API, differentiating between the following situations:
This method consists of using a free API with all the functionalities. However, it has some important limitations:
Its request ratio is limited to at most four requests of any nature per minute.
Requests done by this API have a low priority access for the VirusTotal engine.
In the VirusTotal documentation, they specify that if the user runs a honeyclient, honeypot or any other automation that is going to provide resources to VirusTotal, in other words, not only perform requests, they reward you with a higher request rate quota and special privileges when performing the calls to the API.
VirusTotal also provides a premium Private API where the request rate and total number of queries allowed is only limited by the user’s Terms of Service. Apart from that, it provides a high priority access for requests and more advantages.
For knowing more about VirusTotal’s Terms of Service and using its API you can visit its official documentation.