Many a times, we come across scenarios when the formula tool fails due to the change in the data type of the input fields.
For instance, a numerical calculation would fail or would not give correct result if the data type of a field was changed due to some reason(from double to string for example).
In such cases, we might have to change the change the data type in Select tool or add Tonumber() to the fields expression of the formula tool to make it work.
My proposal is to have a formula tool that should be dynamic to identify the purpose of expression and either add the Tonumber() expression while execution or convert the data type of the fields as per the requirements of the expressions in the formula.