This is actually a neat question to ask, since it applies to other socially-imbued and charged personality traits such as being manipulative, or promiscuous, or other things deemed "less than okay" usually. I see that your main question has already been answered, and Araithiel did an excellent job covering it. If I may, I'd just like to go a little more into my own processes regarding things like this.
I don't think it's a bad thing in writing to start off with an idea such as "I'd like a manipulative character to play the role of a messenger"--in fact, it can be helpful to scaffold and build up other main points of the story. It all comes down to fine-tuning and determining how you will present this to the audience in a way that is believable. That's always the tricky part.
Araithiel's explanation is a fantastic way of going about finding a solution to that problem, but I would also add that it can be inspiring to also look at how other authors and creators have handled a similar character, if you can think of one. That's not to say that you should copy that, but that you should look between the lines and see why what works works and why what doesn't doesn't.
The other thing I'd add is to remember that the audience will need guidance and context in order to understand any character, and the best way to do that is to show rather than to tell. That is, rather than giving exposition, have the character show who they are in action, by making decisions or even facial gestures in response to an event, as opposed to stating something like "Bob felt annoyed." Instead, something like "Bob's eye twitched as he quickly recalculated the situation" gives us more of the character and more of what's going on. You don't have to worry so much about explaining the why all at once since it can unfold for the audience as the actions progress.
I hope this also helps bump your ideas forward, and...wow, welcome to the forum, all of you. I don't think I've met any of you since I've been...less than present lately.