API Search Custom Field

So We have a few custom fields in our Contacts area and I am trying to Search it using the following api URI

https://crm.zoho.com/crm/private/json/Contacts/searchRecords?authtoken=MY_AUTH_KEY&scope=crmapi&criteria=((Deal Date:2/7/2018)AND(Ready To Process?:YES))

It returns the following response

{"response": {"uri":"/crm/private/json/Contacts/searchRecords","error": {"code":4832,"message":"API call cannot be completed as the Criteria parameter contains empty field name"}}}

Please Help!!! It is saying that my field name is empty? That dosent make any sense...

My understanding is that error code 4832 States I am using a TEXT instead of a INTEGER... Not sure why this would be saying this..

Anyone have any Ideas?