Sounds like you might get what you’re looking for with the behavior traverse_errors has when you pass a function with arity 3, referenced briefly in the documentation:
Optionally function can accept three arguments: changeset, field and error tuple {msg, opts}.
It is useful whenever you want to extract validations rules from changeset.validations to build detailed error description.
Combining the first two args using Ecto.Changeset.get_change(changeset, field) will get you the value that triggered the validation error.
