Control request characters

Hi 

I am new user using readyapi 3.5.0   🙂

I have some rest apis with Josn request to test , i need to control the format of every keys value (with string type) in Json request with two main concern:

1- make sure that all the values meet UTF8 encoding standard

2- Check if the characters on the key is only contain these characters

a-zA-Z0-9@+_-.:!#$%&*/=?^_{|}~;

in this case i am going to create test step but i don't know how can i control above concerns ?