Which word best describes someone who is artful and cunning?

The term that best describes someone who is artful and cunning is "wily." This word refers to a person who is skilled at using cleverness or deceit to achieve their goals, often in a way that is subtle and crafty. A wily individual can navigate complex situations with skill, employing guile and intelligence to outsmart others, which aligns perfectly with the concepts of being both artful and cunning.

In contrast, options such as "erratic" describe unpredictable behavior, "strident" conveys a harsh and grating quality, and "cynical" refers to a belief that people are motivated purely by self-interest. None of these terms encapsulates the idea of being clever and resourceful in a strategic manner, which is why "wily" stands out as the most appropriate choice.