IsWeaponSkillType takes one parameter, an Actor Value.
Actor Values are the same parameter type as is taken by the ModActorValue (modav) command. To give you an idea of how it might work. Here is an example of that command:
player.modav luck, -10
"luck" is the Actor Value.
Here are possible Actor Values you can use:
Spoiler
"Aggression"
"Assistance"
"Confidence"
"Energy"
"Responsibility"
"Mood"
"Strength"
"Perception"
"Endurance"
"Charisma"
"Intelligence"
"Agility"
"Luck"
"ActionPoints"
"CarryWeight"
"CritChance"
"HealRate"
"Health"
"MeleeDamage"
"DamageResist"
"PoisonResist"
"RadResist"
"FireResist"
"ElectricResist"
"FrostResist"
"EnergyResist"
"EmpResist"
"SpeedMult"
"Fatigue"
"PerceptionCondition"
"EnduranceCondition"
"LeftAttackCondition"
"RightAttackCondition"
"LeftMobilityCondition"
"RightMobilityCondition"
"BrainCondition"
"Karma"
"XP"
"UnarmedDamage"
"Barter"
"BigGuns"
"EnergyWeapons"
"Explosives"
"Lockpick"
"Medicine"
"MeleeWeapons"
"Repair"
"Science"
"Guns"
"Sneak"
"Speech"
"Survival"
"Unarmed"
"InventoryWeight"
"Paralysis"
"Invisibility"
"Chameleon"
"NightEye"
"Turbo"
"WaterBreathing"
"RadiationRads"
"BloodyMess"
"Variable01"
"Variable02"
"Variable03"
"Variable04"
"Variable05"
"Variable06"
"Variable07"
"Variable08"
"Variable09"
"Variable10"
"IgnoreCrippledLimbs"
"Dehydration"
"Hunger"
"SleepDeprevation"
"DamageThreshold"
Hopefully, you can find your answer by trying some things out with those values.