Yes. The rules explicitly say that "Locations descriptions and object names should be a maximum of TWO words and displayed without an article". You can use articles in your messages, but these will add to the word count. In your example, you could say, "Blue key in room."
Now, imagine how hard it is for me. I'm using the optional two-word limit on ALL messages! So, assuming this is something you've just discovered, I would have to say something like, "See key." or "Find key." or "Discover key." The fact that it's in the room is implied and the fact that it's blue is in the object description.