Is there a rule for number of variables and characters used in a function
 

Hello,

We have a custom function that uses 29 variables as input. We tried 30 but
it would not work.

It works with 29 but now when we select the function using the "paste
function" button we get no variable names to the left. I found that if I
reduce the total number of characters in the variable names combined to less
than 214, it works.

Is there a rule that says how many variables are allowed in a function AND
how many characters are allowed?

thanks - it will help us with future projects.