AGENT Get sheet + Function tools not working together..

Hello, i am Stuck for days in this (there are no tutorials or anything..). Setting AI agent for financcial agency. I cant get toh´gether tool get sheet - there are actual % of selected banks morgages. The agency want to have control over this + it is very dynamic. And after this, i have added Function tool - it is for calculating the yearly € saved. The get sheet tool is sucessful and the agent can answer exact numbers from there, however it can not wrap it to the variable correctly (i need the variable as a string text (i think it it the best way) to the calculator) Are there any ways to deal with this? Please i am already HOPELESS :/

I WILL GLADLY ADD MORE PICTURES