Preheat an air fryer to 400 degrees F (200 degrees C) according to manufacturer's instructions.

Whisk mustard, brown sugar, parsley, thyme, salt, and pepper together in a large bowl. Place tenderloin into the bowl and roll through the mustard mixture until evenly coated on all sides.

Place potatoes, green beans, and olive oil into a separate bowl. Season with salt and pepper to taste and stir until evenly combined. Set aside.

Place tenderloin into the basket of the preheated air fryer and cook, undisturbed, until slightly pink in the center, about 20 minutes. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C). Transfer to a cutting board and let rest for 10 minutes.

Meanwhile, place green beans and potatoes into the air fryer basket and cook for 10 minutes, shaking halfway through cook time.

Slice tenderloin and serve with potatoes and green beans.