Datum placement tolerance

When measuring a machined datum feature like a hole or slot what positional tolerance applies?

What do you reference for positional tolerance of the machined datum feature?

Since the datum features place the position of other machined features; I’ve found that you can have a part which measures good, but is functional out of tolerance if the machined datum feature is misplaced (datums: three target points, two target points, and slot)

I’ve since been trying to hold the datum features to a tight positional tolerance referenced to the closest part edge to ensure the part remains functionally correct. But I have not idea what tolerance I really should apply to the datum features and what to reference the position to. (Nothing on the drawings for the datum features)

Typically run into a few datum feature types where this comes up 1) three target points, two target points, and slot 2) Four target points, hole, slot 3) Two planes, and a slot 4) Plane, hole, slot