Equip Spells and Equip Cards

Equip scripting has two sides:

1. The card must become equipped to a monster.
2. The Equip Card registers effects that apply while it remains equipped.

MDPro4/YGOPro exposes the equip action through Duel.Equip. Local utility scripts also provide Auxiliary.AddEquipSpellEffect, which builds the common Equip Spell activation effect and EFFECT_EQUIP_LIMIT for you.

Some outside examples use helper names that do not exist in this local script set. In MDPro4, the standard Equip Spell helper is Auxiliary.AddEquipSpellEffect, and many cards still write the activation, equip limit, and operation by hand when the card has extra state to manage.

Pick The Equip Shape First

Before writing the filter, decide what kind of equip flow the card actually uses.

Card text shape	Local pattern to start from
"Activate this card by targeting 1 face-up monster..."	Use Auxiliary.AddEquipSpellEffect or the manual activation pattern below.
"Special Summon that target, then equip this card to it"	Target the monster in its source location, Special Summon it, then call Duel.Equip and register a limit during resolution.
"Equip 1 appropriate card from your GY/Deck/banished cards"	Select or target the card to become equipped, check zone availability, CheckEquipTarget, uniqueness, and forbidden state before Duel.Equip.
"Equip several cards at once"	Use stepped Duel.Equip(..., true, true) calls, then finish with Duel.EquipComplete().
"Place this monster in the Spell & Trap Zone as a Continuous Spell"	Use Duel.MoveToField and type-changing effects instead of equip APIs.

This first choice prevents a common beginner mistake: writing every "put in the Spell & Trap Zone" effect as an Equip Spell. Equip state is a relationship between two cards; MoveToField is just a field-placement action.

Manual Equip Spell Pattern

The local script style for a basic Equip Spell is:

local e1=Effect.CreateEffect(c)
e1:SetCategory(CATEGORY_EQUIP)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetCode(EVENT_FREE_CHAIN)
e1:SetProperty(EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_CONTINUOUS_TARGET)
e1:SetTarget(s.target)
e1:SetOperation(s.operation)
c:RegisterEffect(e1)

The target function selects a face-up monster and announces that the card will be equipped.

function s.eqfilter(c)
    return c:IsFaceup() and c:IsSetCard(0x1034)
end

function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
    if chkc then return chkc:IsLocation(LOCATION_MZONE) and s.eqfilter(chkc) end
    if chk==0 then
        return Duel.IsExistingTarget(s.eqfilter,tp,LOCATION_MZONE,LOCATION_MZONE,1,nil)
    end
    Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_EQUIP)
    Duel.SelectTarget(tp,s.eqfilter,tp,LOCATION_MZONE,LOCATION_MZONE,1,1,nil)
    Duel.SetOperationInfo(0,CATEGORY_EQUIP,e:GetHandler(),1,0,0)
end

During resolution, recheck both the Equip Card and the target monster.

function s.operation(e,tp,eg,ep,ev,re,r,rp)
    local c=e:GetHandler()
    local tc=Duel.GetFirstTarget()
    if c:IsRelateToEffect(e) and tc and tc:IsRelateToEffect(e) and tc:IsFaceup() then
        Duel.Equip(tp,c,tc)
    end
end

This is the same shape used by local Equip Spell scripts such as the one that registers an ATK bonus and an equip limit after its activation effect.

Activation Shapes

Not every effect that equips a card uses the same target shape.

Shape	Targeting pattern	Equip timing
Ordinary Equip Spell activation	EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_CONTINUOUS_TARGET, Duel.SelectTarget on a face-up monster	Duel.Equip during the activation's operation
Effect that Special Summons, then equips itself	Usually targets the monster in the GY/banished/other source location, without EFFECT_FLAG_CONTINUOUS_TARGET	Special Summon first, then Duel.Equip and register the equip limit
Monster or Trap becoming an Equip Card	Often non-activation or monster-effect flow	Duel.Equip changes the card into equip state and the script adds limits/effects
Existing Equip Card moving to a new monster	Target or select the new monster and check CheckEquipTarget	Duel.Equip changes the equip relationship

An effect does not target just because it will equip something. In script terms, targeting comes from the effect property and target APIs. Duel.Equip creates the equip relationship during resolution; it does not retroactively make a non-targeting effect into an activation-time targeting effect.

Rules-Facing Script Notes

Equip Cards are unusually sensitive to the difference between "this card is legally equipped" and "this card's continuous effect is currently applying." Keep these ideas separate:

Topic	Script consequence
Activation and targeting	Normal Equip Spell activation targets a face-up monster and uses continuous targeting flags.
Equip legality	EFFECT_EQUIP_LIMIT or Union state decides which monster the card may remain equipped to.
Effect application	EFFECT_TYPE_EQUIP applies effects to the equipped monster while the equip state is valid.
Leaving the field	Equip effects stop applying when the Equip Card is no longer equipped/face-up in the expected state.
Negation	A negated activation does not complete the equip operation; negated continuous equip effects do not apply their bonus.

The script should not treat a failed stat bonus as the same thing as an illegal equip target. For example, a monster might be unaffected by a continuous equip modifier while the Equip Card itself is still legally equipped. The equip limit answers the legal-target question.

What The Core Handles

Local core behavior does a lot of equip housekeeping for scripts:

• If Duel.Equip cannot keep the Equip Card on the field because the target is not a face-up monster or there is no usable Spell & Trap Zone, the Equip Card is sent to the GY by rule.
• When a card becomes equipped and it was not already an Equip Spell, the core adds the temporary type-change support needed for equip state.
• If the equipped monster leaves the field or the equip relationship is lost, local core destroys the Equip Card with REASON_RULE+REASON_LOST_TARGET.
• If the equipped monster remains but no longer satisfies EFFECT_EQUIP_LIMIT, the core destroys the Equip Card by rule during adjustment.

That means ordinary equip scripts do not need to manually poll the equipped monster every frame. They do need to register the correct equip limit and use the correct reason checks when a later trigger cares why the Equip Card left.

Equip Effects

An Equip Card's bonus is usually an EFFECT_TYPE_EQUIP effect. It applies to the equipped monster, not to the Equip Card itself.

local e2=Effect.CreateEffect(c)
e2:SetType(EFFECT_TYPE_EQUIP)
e2:SetCode(EFFECT_UPDATE_ATTACK)
e2:SetValue(800)
c:RegisterEffect(e2)

Dynamic equip values use a value function. Local scripts use this for Equip Cards whose bonus depends on counters, equipped state, or other live data.

function s.atkval(e,c)
    return e:GetHandler():GetCounter(0x1)*500
end

EFFECT_TYPE_EQUIP is already tied to equip state, so a normal equip modifier does not need SetRange(LOCATION_SZONE). If the equipped monster cannot use a particular continuous value, such as a DEF update on a Link Monster, the modifier simply has no useful result for that monster; it is not automatically the same as an illegal equip target.

Equip Limits

Most Equip Cards also register EFFECT_EQUIP_LIMIT as a single effect. The limit tells the engine which equipped monster remains legal for that card.

local e3=Effect.CreateEffect(c)
e3:SetType(EFFECT_TYPE_SINGLE)
e3:SetCode(EFFECT_EQUIP_LIMIT)
e3:SetProperty(EFFECT_FLAG_CANNOT_DISABLE)
e3:SetValue(s.eqlimit)
c:RegisterEffect(e3)

function s.eqlimit(e,c)
    return c:IsSetCard(0x1034)
end

Card.CheckEquipTarget(c1,c2) checks whether c2 is a valid equipped monster for c1; the local define comments note that this is determined by EFFECT_EQUIP_LIMIT or Union state.

function s.filter(c,e,tp,ec)
    return c:IsSetCard(0x207a)
        and c:IsCanBeEffectTarget(e)
        and c:CheckEquipTarget(ec)
end

Use CheckEquipTarget when a script is moving an existing Equip Card to a new monster or choosing a target for a card that already has equip-limit logic.

Target Filter vs Equip Limit

The activation target filter and the equip-limit function answer different questions.

Function	When it is checked	Question
Target filter	Activation or selection time	"Can this monster be chosen for this effect right now?"
Equip limit	While the card is equipped	"May this Equip Card remain equipped to this monster?"

The local Auxiliary.AddEquipSpellEffect helper can keep those aligned for a normal Equip Spell. It builds the activation target from the filter, registers EFFECT_EQUIP_LIMIT, and rechecks the limit before Duel.Equip.

When the equip flow is unusual, write the checks by hand. Local c11802691.lua checks the candidate Equip Card with CheckEquipTarget, CheckUniqueOnField, and IsForbidden before offering the player a choice between equipping it and sending it to the GY. Local c10204849.lua registers a temporary equip limit only after the target monster is Special Summoned and Duel.Equip has been called during resolution.

Auxiliary.AddEquipSpellEffect

The local utility.lua helper Auxiliary.AddEquipSpellEffect creates a common Equip Spell activation effect with:

• CATEGORY_EQUIP
• EFFECT_TYPE_ACTIVATE
• EVENT_FREE_CHAIN
• EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_CONTINUOUS_TARGET
• a target function using Duel.IsExistingTarget and Duel.SelectTarget
• an operation that calls Duel.Equip
• an EFFECT_EQUIP_LIMIT effect on the Equip Card

Use the helper when the card follows that normal shape. Write the activation manually when the card has unusual targeting, delayed equipping, multiple possible equipped monsters, or extra state to store.

Cards Equipped by Effects

Monsters can also become Equip Cards through card effects. Those scripts still use the same core ideas:

• move or equip the card with Duel.Equip or a helper that wraps it
• register an equip limit or Union limit
• register EFFECT_TYPE_EQUIP bonuses or replacement effects
• recheck that the card and target are still related to the resolving effect

If a monster is moved into the Spell & Trap Zone as a Continuous Spell/Trap instead of becoming equipped, that is a different action. Local scripts use Duel.MoveToField and then register a type-changing effect such as EFFECT_CHANGE_TYPE.

Duel.MoveToField(tc,tp,tp,LOCATION_SZONE,POS_FACEUP,true)
local e1=Effect.CreateEffect(e:GetHandler())
e1:SetType(EFFECT_TYPE_SINGLE)
e1:SetCode(EFFECT_CHANGE_TYPE)
e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE)
e1:SetReset(RESET_EVENT+RESETS_STANDARD)
e1:SetValue(TYPE_SPELL+TYPE_CONTINUOUS)
tc:RegisterEffect(e1)

That pattern creates a Continuous Spell/Trap style card on the field. It is not the same as Duel.Equip.

Activated Effects On Equip Cards

An Equip Card can have activated effects in addition to its equip modifiers. Those effects use their own SetType, SetRange, and callbacks.

local e1=Effect.CreateEffect(c)
e1:SetDescription(aux.Stringid(id,0))
e1:SetType(EFFECT_TYPE_IGNITION)
e1:SetRange(LOCATION_SZONE)
e1:SetTarget(s.target)
e1:SetOperation(s.operation)
c:RegisterEffect(e1)

When an activated effect needs the currently equipped monster, read it from the Equip Card.

local ec=e:GetHandler():GetEquipTarget()
if ec and ec:IsFaceup() then
    -- use the equipped monster
end

When the effect needs the monster that was equipped before the Equip Card left the field, local scripts use Card.GetPreviousEquipTarget.

local ec=e:GetHandler():GetPreviousEquipTarget()

This is useful for "if this equipped card is sent..." style effects.

Local c11913700.lua shows the common lost-target trigger shape:

function s.spcon(e,tp,eg,ep,ev,re,r,rp)
    local ec=e:GetHandler():GetPreviousEquipTarget()
    return e:GetHandler():IsReason(REASON_LOST_TARGET)
        and ec and not ec:IsLocation(LOCATION_ONFIELD+LOCATION_OVERLAY)
end

Use GetPreviousEquipTarget for this kind of trigger because by the time the Equip Card is in the GY, GetEquipTarget no longer describes the old relationship.

Continuous Card Targets

Equip state is not the only long-term relationship a card can keep. Some local scripts use card targets for continuous relationships and read them with GetFirstCardTarget.

local tc=e:GetHandler():GetFirstCardTarget()

Use the equip APIs for true equip relationships. Use card-target APIs only when the local script pattern or the card text establishes a continuous target that is not simply "this card is equipped to that monster."

Summon-Then-Equip Effects

Some effects Special Summon a monster, then equip a card to that monster. These effects should only register the equip limit after Duel.Equip succeeds.

if Duel.SpecialSummon(tc,0,tp,tp,false,false,POS_FACEUP)>0
    and Duel.Equip(tp,c,tc) then
    local e1=Effect.CreateEffect(c)
    e1:SetType(EFFECT_TYPE_SINGLE)
    e1:SetCode(EFFECT_EQUIP_LIMIT)
    e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE)
    e1:SetValue(s.eqlimit)
    c:RegisterEffect(e1)
end

Local c10204849.lua uses this category: it targets a monster in the GY, Special Summons it, then equips the Spell to that monster and registers the equip limit during resolution. That is why the activation effect uses ordinary card targeting for the GY monster, not the continuous target flag used by a normal Equip Spell activation.

If the later card text destroys or sends the equipped monster when the Equip Card leaves, store or read the relevant equip/card target relationship and recheck it during that later operation.

Stepped Equip

The local define file shows optional stepped behavior:

Duel.Equip(player,c1,c2,up,is_step)
Duel.EquipComplete()

When is_step is true, the equip process is split and must be completed with Duel.EquipComplete(). This is for scripts that need several equip operations to finish as one process.

Local c10613952.lua uses this shape after selecting several cards from the GY: it checks the available Spell & Trap Zones, equips each selected card with Duel.Equip(tp,tc,c,true,true), then calls Duel.EquipComplete() once after the loop. Most ordinary Equip Spells call Duel.Equip without the stepped argument.

Local Scripts To Read

These scripts are useful when you need a concrete local pattern instead of a generic template.

Script	Why it is useful
c1435851.lua	Small ordinary Equip Spell using the local aux.AddEquipSpellEffect helper.
c10204849.lua	Targets a monster, Special Summons it, equips the Spell to it, then registers EFFECT_EQUIP_LIMIT during resolution.
c10613952.lua	Equips several cards with stepped Duel.Equip calls and finishes with Duel.EquipComplete().
c11802691.lua	Checks CheckEquipTarget, CheckUniqueOnField, and IsForbidden before equipping cards chosen from another location.
c11913700.lua	Uses GetPreviousEquipTarget for a lost-target trigger after the Equip Card leaves the field.

When you see an equip helper name that is not in the local API, use this table as the starting point. The MDPro4 scripts above show the behavior that exists in this repository.

Common Pitfalls

Mistake	Safer pattern
Equipping without checking the Spell & Trap Zone or target relation.	Check activation legality, then recheck IsRelateToEffect in operation.
Letting the target filter and equip limit drift apart accidentally.	Keep them aligned through Auxiliary.AddEquipSpellEffect, or document the reason and recheck the limit before Duel.Equip.
Choosing a card to become an Equip Card without zone and field-state checks.	Check Duel.GetLocationCount, CheckUniqueOnField, IsForbidden, and CheckEquipTarget when the local pattern does.
Registering only the ATK/DEF bonus.	Also register EFFECT_EQUIP_LIMIT when the card needs a legal equipped monster.
Treating an Equip effect as EFFECT_TYPE_SINGLE.	Use EFFECT_TYPE_EQUIP for effects applied to the equipped monster.
Moving a monster to the Spell & Trap Zone when the card should be equipped.	Use Duel.Equip for equip state; use Duel.MoveToField for Continuous Spell/Trap state.
Checking GetEquipTarget after the Equip Card has already left the field.	Use GetPreviousEquipTarget in leave-field or sent-to-GY triggers.
Assuming a non-applying equip bonus means the equip itself is illegal.	Separate equip legality from whether a specific continuous effect can affect that monster.

Useful API pages:

• Duel.Equip
• Duel.EquipComplete
• Duel.MoveToField
• Card.GetEquipTarget
• Card.GetPreviousEquipTarget
• Card.GetEquipGroup
• Card.CheckEquipTarget
• Card.GetFirstCardTarget
• Effect.SetType
• Effect.SetValue