Steve Portigal and Niti Bhan look at things from across the table:
Design can be brought in as a service, but it's important to remember that it's a creative service.
Designers are smart and talented people who typically do "think out of
the box" (a phrase more derided inside the design community than
outside, yet still requested in more initial meetings than you can
imagine). So although your desired outcome may be very specific, the
designer's process to delivering your outcome will inevitably involve
challenging its very foundations. Here's an illustration:
Q: How many designers does it take to change a light bulb? A: Does it have to be a light bulb?