mrbrightsides: i strongly urge you to bring this discrepancy to the attention of the firm sending the letter. use this as an excuse to extend the dialogue in a positive way and to clarify mutual expectations. I resonably sure they will appreciate your attention to detail and it may just be that they used the wrong form letter to extend your offer.

it's very important that the offer letter explain clearly the mutual expectations and responsibilities of the two parties and that the letter accurately represent the situation. whenever there is ambuiguity or mis-understanding at this stage, it almost always leads to difficulties downstream. make sure everybody has the same understanding before you start work...and get that understanding documented accurately

good luck.

I agree with quizzical. Bringing this up early shows that you're proactive. Also, in this profession, no employer likes to hear employees say "that's not in my job description" - which is something you might find yourself saying in a few months if you don't clarify the expectations now.

I had someone hire me for a programmer's job when I thought I was being hired as a designer. It took about three months for us to straighten out the discrepancy, and, while it led to a fairly nice severance, I was out of a job when all was said and done.

Yep - quizzical and DCA are right, bring it up now, and do it in a positive way: tell them you are confident you can perform the work of the wrong offer, but you want to make sure you're not being judged on the wrong set of expectations. They should be, as said, happy with your attention to detail, honesty, and confidence. Good luck.