Although the word "brief" is commonly used to mean short in time or saying little, in this instance it does not.  Brief in this usage is relating to the instructions you have been given by a client or the intended solution to the problem you have identified in your "Situation".   Putting the two words together design and brief, you must produce a Design Brief that describes your task.

I think that all design brief's should start in the same way and then become specific to your stated problem.  Start by saying;

To design, make test and evaluate ................ and now be specific to your problem.

To design, make test and evaluate a jewellery box ....................  well that's OK, but I think, if you use the words "jewellery box"  you immediately have in your mind's eye a pre-conceived conventional box.  Nothing wrong with that, but if you change the words slightly, you just might give your imagination a little more room to find a really new and great idea.

 To design, make test and evaluate a storage system for jewellery .................. now a storage system can be a box, it can also be a Tesco's bag that hangs on a door handle, it can be diamond covered casket, a felt roll or whatever your imagination can come up with.  A CD storage system can be a box, a floor standing rack, a wall mounted shelf or a hanging basket.  All store CD's or jewellery.

Now personalise to suit your client's wishes for solving the problem in the Situation.