Caps are always risky... even if someone has had one that matches your description, chances are it won't be the same. So no one can give you a accurate opinion on them.
If they are meant to be only mdma, they won't be completely filled with powder. How full are they?
If it's white powder and brown speckles, it might be a combination of stuff. Personally I would ALWAYS test a cap before having it, it's even more important if it clearly contains more than one substance. For example, the brown could be crushed up mdma pills, and the white powder could be ketamine or speed.
I learned the hard way that caps (even from reliable sources) can be dodgy, so be careful!