Deep down, Clary knows she has Jace wrapped around her finger. Look at that coy look she's giving him. She knows she'll get what she wants. These two just like playing games with each other.
Jace knows Clary isn't going to just sit back and do nothing, no matter how much of a hard look he gives her. I think he just enjoys watching her try to plead her case.
Magnus probably just wanted a nice, relaxing night at his club. Instead, shadowhunters show up and trouble follows. Has Valentine found them? Will Jace be able to stop him?
Don't get me wrong. I'm totally grateful that your friends got me out before the vampires drained me like a Big Gulp, but how well do you know this Jace guy.