The other day I was playing a one-off under another DM and he did something that I found a bit off-putting; he would give players various options and then tell us exactly what we needed to succeed, and to what degree it would be effective. To me, this was utterly baffling. What I'm wondering is this: exactly how much of the mechanics do you 'let on' to your PCs? Also, for the players, does this seem like a weird practice and would you want your DM to adopt it?