More Descriptive Custom Field Error Messages for Numeric/Currency Fields

The single line & paragraph text fields have the option for the answer format to be text, number or currency, which is great. However, if a user tries filling in a text value for a numeric format field, there is no error message letting the user know why they are not able to fill in text and therefore they think the form is broken. If the field is required, it just says it's a required field. So to prevent confusion, I need to add 'numeric value only' to the custom form question text, for example. Would be really helpful if WF can simply have more descriptive error messages - if someone tries using alpha for a numeric field, show a message with 'Please fill in numbers only.' Right now there is no message unless it's required and the user has no idea why they can't fill in an answer.