The men entered the shop on Thornhill Road at about 8.25pm yesterday with a sword, described as approximately 12 inches in length, ornate, and Samurai-style with a black and gold handle, demanding a member of staff open the tills.
The staff member was not physically hurt during the incident and the men fled on foot.
Three men were seen fleeing onto Leslie Road and drove off in a blue car towards Hardwick Road.
Two are described as wearing dark clothing with their hoods up. A third man was said to be wearing a grey hoodie with a stripe down the side.
Detectives are asking people who were in the area at the time to check their dash-cam footage for this vehicle.
Anyone with any information should message Staffordshire Police on Facebook or Twitter quoting incident number 643 of 17 January, call 101 or alternatively contact Crimestoppers anonymously on 0800 555 111.