The runningBalance parameter of Yodlee is always the current balance, or the previous statement balance. Is there any way to tell whether the person is not paying the balance in full and incurring interest charges?
RunningBalance is always the current balance. For credit cards Yodlee do provide statements which has the information about the statement balance(Amount due).Yodlee also scrapes the Last payment amount. This can be used if the person has paid the total amount in one shot. But if the person has made part payments then transactions can be used to determine if the person has paid the complete amount due or is incurring some interest charges for not paying the complete amount due.
Please check the data model pages which gives an overview of data elements scraped - Mani page -https://developer.yodlee.com/Indy_FinApp/Aggregation_Services_Guide/Data_Model
Card Statement - https://developer.yodlee.com/Indy_FinApp/Aggregation_Services_Guide/Data_Model/Card_Statement_Data
Card Account - https://developer.yodlee.com/Indy_FinApp/Aggregation_Services_Guide/Data_Model/Card_Account_Data
Card Transaction - https://developer.yodlee.com/Indy_FinApp/Aggregation_Services_Guide/Data_Model/Card_Transaction_Data