Specs

valid?(any()) :: boolean()

Simply checks if the given term is ok- or error-tuple.

Using this function you can write e.g. r :: v[Croma.Result.t(integer)] in your parameter list of defun macro to validate r is of type t/0. However note that this function only checks the outmost structure of an argument; 2nd value in the 2-tuple won't be validated for the given type parameter (in the above example it won't verify whether r contains an integer or not).