I should add that for the true mapo tofu experience you need 辣豆瓣酱 (là dòu bàn jiàng). Variations of doubanjiang are made all over China (and doubtlessly elsewhere), but the one you want for mapo tofu is this one. The 辣 (là) means 'hot' as in 'spicy'.
Sometimes it may also be labelled 红油 (hóng yóu) which indicates it contains chili oil.
The most recommended brand is:
Pixian Doubanjiang. Pixian is a city in Sichuan famed for its high quality doubanjiang. It is sold internationally, both in jars and in these plastic pouches.
Another excellent brand, also from Pixian is Juancheng doubanjiang. I'm not sure how internationally that is sold, but in the USA, Mala Market stock it..
Juancheng Dobanjiang
Others can be very unspicy, especially the Cantonese variety.