Expression may not be longer than 4,000 characters. You have entered 6,811 characters

I have created a Process Model with Start a Process Template. My Process Model has around 58 Process Variabes but through WEBApi when i try to pass those details, Web Api Throws an error like

"Expression may not be longer than 4,000 characters. You have entered 6,811 characters."

what can be done to overcome this?

Thanks,

Sakthi S.