If you are using the V1, the rate limit is 1000 calls/hour. 


On the V2, the following rates will apply:


Plan    
Calls per hour allowed
Sprout
1000
Blossom and Garden
3000
Estate and Forest    
5000


If you are looking to increase your API limit, please drop an email to support@freshdesk.com with a complete description of your use-case and we'll help you sort this out.