As an Ensign (immediate graduate), the job descriptions are fairly limited, but they expand for the second tour as a LTJG.
Right out of the Academy you could:
Be a Deck Watch Officer (DWO) serving on a variety of cutters. Some are white hulled and have a focus on law enforcement. Others are black and focus on buoy tending. Then we have red ones that focus on ice breaking. However, the Coast Guard is a multi-mission service, so you could be saving lives at sea one day, boarding a ship on another, or interdicting migrants on yet another. Most Academy graduates become DWO's for their first tour.
Become an Engineering Officer in Training (EOIT), otherwise known as student engineers. You will be responsible for ensuring that the engines and auxilary systems on the cutter are operational and in working order.
Be assigned to flight training. Have dreams of taking to the skies and plucking people out of the water? For many (myself included), this was the big draw to the USCGA. Around 10% of the graduating class can be assigned to flight training, but you can still apply for flight school at your first unit if you don't get it the first time around.
Sector- Prevention and Response. These jobs are on land and involved maritime safety and security. Unfortunately I don't know too much about these jobs since the Academy doesn't tell us much about them. Typically 5% of the class will be assigned to a sector.
Your options explode for the second tour as a LTJG. You could go to flight school! You could become the CO of an 87' patrol boat! You could deploy to Bahrain and serve as OPS or XO on a 110' patrol boat. Grad School! There's an exchange program with the Navy where you serve on a Navy ship. You could go to the Tactical Law Enforcement Team, and be in charge of Law Enforcement Detachments (LEDETs) while deployed/attached to a Navy vessel.