Automation Reference

This page details the structure of Avrae’s Automation system, the backbone behind custom spells and attacks.

Basic Structure

An automation run is made up of a list of effects (AKA automation node), each of which may have additional effects that it runs under certain conditions. This recursive structure is called the automation tree.

Glossary

automation engine: The Automation Engine is the code responsible for reading the automation tree and executing it against the current game state. It handles rolling the dice, checking against your targets’ armor classes, modifying hit points, and other game mechanics.

automation tree
automation: The automation tree (sometimes just called “automation”) is the program that the Automation Engine runs. It’s made up of multiple nodes that all link together to make an attack, action, spell, or more.

effect
node: A single step of automation - usually, this is a D&D game mechanic like rolling to hit, making a saving throw, or dealing damage, but this can also be used in more programmatic ways to help set up other nodes.

Runtime Variables

All Automation runs provide the following variables:

caster (AliasStatBlock) The character, combatant, or monster who is running the automation.
targets (list of AliasStatBlock, str, or None) A list of combatants targeted by this automation (i.e. the -t argument).

Additionally, runs triggered by an initiative effect (such as automation provided in a ButtonInteraction) provide the following variables:

ieffect (SimpleEffect) The initiative effect responsible for providing the automation.

Target

{
    type: "target";
    target: "all" | "each" | int | "self" | "parent" | "children";
    effects: Effect[];
    sortBy?: "hp_asc" | "hp_desc";
}

A Target effect should only show up as a top-level effect. It designates what creatures to affect.

class Target

target

"all" or "each" (actions only): Affects each of the given (by the -t argument) targets.
int (actions only): Affects the Nth target (1-indexed).
"self": Affects the caster, or the actor the triggering effect is on if run from an IEffect button.
"parent" (IEffect buttons only): If the triggering effect has a parent effect, affects the actor the parent effect is on.
"children" (IEffect buttons only): If the triggering effect has any children effects, affects each actor a child effect is on.

effects: A list of effects that each targeted creature will be subject to.

sortBy

optional - Whether to sort the target list. If not given, targets are processed in the order the -t arguments are seen. This does not affect self targets.

hp_asc: Sorts the targets in order of remaining hit points ascending (lowest HP first, None last).
hp_desc: Sorts the targets in order of remaining hit points descending (highest HP first, None last).

Variables

target (AliasStatBlock) The current target.
targetIteration (int) If running multiple iterations (i.e. -rr), the current iteration (1-indexed).
targetIndex (int) The index of the target in the list of targets processed by this effect (0-indexed - first target = 0, second = 1, etc.). Self targets, nth-targets, and parent targets will always be 0.
targetNumber (int) Same as targetIndex, but 1-indexed (equivalent to targetIndex + 1).

Attack

{
    type: "attack";
    hit: Effect[];
    miss: Effect[];
    attackBonus?: IntExpression;
    adv?: IntExpression;
}

An Attack effect makes an attack roll against a targeted creature. It must be inside a Target effect.

Attack:

hit: A list of effects to execute on a hit.

miss: A list of effects to execute on a miss.

attackBonus: optional - An IntExpression that details what attack bonus to use (defaults to caster’s spell attack mod).

adv: optional - An IntExpression that details whether the attack has inherent advantage or not. 0 for flat, 1 for Advantage, 2 for Elven Accuracy, -1 for Disadvantage (Default is flat).

Variables

lastAttackDidHit (bool) Whether the attack hit.
lastAttackDidCrit (bool) If the attack hit, whether it crit.
lastAttackRollTotal (int) The result of the last to-hit roll (0 if no roll was made).
lastAttackNaturalRoll (int) The natural roll of the last to-hit roll (e.g. 10 in 1d20 (10) + 5 = 15; 0 if no roll was made).
lastAttackHadAdvantage (int) The advantage type of the last to-hit roll. 0 for flat, 1 for; Advantage, 2 for Elven Accuracy, -1 for Disadvantage

Save

{
    type: "save";
    stat: "str" | "dex" | "con" | "int" | "wis" | "cha";
    fail: Effect[];
    success: Effect[];
    dc?: IntExpression;
    adv?: -1 | 0 | 1;
}

A Save effect forces a targeted creature to make a saving throw. It must be inside a Target effect.

class Save

stat: The type of saving throw.

fail: A list of effects to execute on a failed save.

success: A list of effects to execute on a successful save.

dc: optional - An IntExpression that details what DC to use (defaults to caster’s spell DC).

adv: optional, default 0 - Whether the saving throw should have advantage by default (-1 = disadvantage, 1 = advantage, 0 = no advantage).

Variables

lastSaveDidPass (bool) Whether the target passed the save.
lastSaveDC (int) The DC of the last save roll.
lastSaveRollTotal (int) The result of the last save roll (0 if no roll was made).
lastSaveNaturalRoll (int) The natural roll of the last save roll (e.g. 10 in 1d20 (10) + 5 = 15; 0 if no roll was made).
lastSaveAbility (str) The title-case full name of the ability the save was made with (e.g. "Strength", "Wisdom", etc).

Damage

{
    type: "damage";
    damage: AnnotatedString;
    overheal?: boolean;
    higher?: {int: string};
    cantripScale?: boolean;
}

Deals damage to or heals a targeted creature. It must be inside a Target effect.

Note

This node can also be used to heal a target; simply use negative damage to supply healing.

class Damage

damage: How much damage to deal.

overheal: New in version 1.4.1.

optional - Whether this damage should allow a target to exceed its hit point maximum.

higher: optional - How much to add to the damage when a spell is cast at a certain level.

cantripScale: optional - Whether this roll should scale like a cantrip.

Variables

lastDamage (int) The amount of damage dealt.

TempHP

{
    type: "temphp";
    amount: AnnotatedString;
    higher?: {int: string};
    cantripScale?: boolean;
}

Sets the target’s THP. It must be inside a Target effect.

class TempHP

amount: How much temp HP the target should have.

higher: optional - How much to add to the THP when a spell is cast at a certain level.

cantripScale: optional - Whether this roll should scale like a cantrip.

Variables

lastTempHp (int) The amount of temp HP granted.

IEffect

{
    type: "ieffect2";
    name: string;
    duration?: int | IntExpression;
    effects?: PassiveEffects;
    attacks?: AttackInteraction[];
    buttons?: ButtonInteraction[];
    end?: boolean;
    conc?: boolean;
    desc?: AnnotatedString;
    stacking?: boolean;
    save_as?: string;
    parent?: string;
}

Adds an InitTracker Effect to a targeted creature, if the automation target is in combat. It must be inside a Target effect.

Note

If the targeted creature is not in combat, this will display the effects of the initiative effect but not save it on the creature.

class IEffect

name: The name of the effect to add.

duration: optional, default infinite - The duration of the effect, in rounds of combat. If this is negative, creates an effect with infinite duration.

effects: optional, default no effects - The effects to add. See PassiveEffects.

attacks: optional, default no attacks - The attacks granted by this effect. See AttackInteraction.

buttons: optional, default no buttons - The buttons granted by this effect. See ButtonInteraction.

end: optional, default false - Whether the effect timer should tick on the end of the turn, rather than start.

conc: optional, default false - Whether the effect requires concentration.

desc: optional - The description of the effect (displays on combatant’s turn).

stacking: optional, default false - If true and another effect with the same name is found on the target, instead of overwriting, add a child effect with name {name} x{count} and no description, duration, concentration, attacks, or buttons.

save_as: optional, default None - If supplied, saves an IEffectMetaVar to the automation runtime, which can be used in another IEffect’s parent key to set its parent to this effect. Must be a valid identifier.

parent

optional, default None - If supplied, sets the created effect’s parent to the given effect. This must be the name of an existing IEffectMetaVar.

If parent is supplied but the parent effect does not exist, will not set a parent.

If conc is true, the given parent effect will take priority over the concentration effect.

If stacking is true and a valid stack parent exists, the stack parent will take priority over the given parent.

Variables

(supplied save_as) (IEffectMetaVar or None) A reference to the effect that was added to the target. Use this in another IEffect’s parent key to set that IEffect’s parent to the given one.

PassiveEffects

{
    attack_advantage: IntExpression;
    to_hit_bonus: AnnotatedString;
    damage_bonus: AnnotatedString;
    magical_damage: IntExpression;
    silvered_damage: IntExpression;
    resistances: AnnotatedString[];
    immunities: AnnotatedString[];
    vulnerabilities: AnnotatedString[];
    ignored_resistances: AnnotatedString[];
    ac_value: IntExpression;
    ac_bonus: IntExpression;
    max_hp_value: IntExpression;
    max_hp_bonus: IntExpression;
    save_bonus: AnnotatedString;
    save_adv: AnnotatedString[];
    save_dis: AnnotatedString[];
    check_bonus: AnnotatedString;
    check_adv: AnnotatedString[];
    check_dis: AnnotatedString[];
}

Used to specify the passive effects granted by an initiative effect.

class PassiveEffects

attack_advantage: optional, default no advantage - Whether this effect gives the combatant advantage on all attacks. -1 for dis, 1 for adv, 2 for elven accuracy.

to_hit_bonus: optional - A bonus that this effect grants to all of the combatant’s to-hit rolls.

damage_bonus: optional - A bonus that this effect grants to all of the combatant’s damage rolls.

magical_damage: optional, default false - Whether this effect makes all of the combatant’s attacks do magical damage. 0 for false, anything else for true.

silvered_damage: optional, default false - Whether this effect makes all of the combatant’s attacks do silvered damage. 0 for false, anything else for true.

resistances: optional - A list of damage types and optionally modifiers (e.g. “fire”, “nonmagical slashing”) that the combatant should be resistant to while this effect is active.

immunities: optional - A list of damage types and optionally modifiers (e.g. “fire”, “nonmagical slashing”) that the combatant should be immune to while this effect is active.

vulnerabilities: optional - A list of damage types and optionally modifiers (e.g. “fire”, “nonmagical slashing”) that the combatant should be vulnerable to while this effect is active.

ignored_resistances: optional - A list of damage types and optionally modifiers (e.g. “fire”, “nonmagical slashing”) that the combatant should not be resistant, immune, or vulnerable to while this effect is active.

ac_value: optional - A value to set the combatant’s armor class to while this effect is active.

Note

If both ac_value and ac_bonus are specified, the resulting value will be equal to ac_value + ac_bonus.

If multiple effects specify ac_value, the highest value will be used.

ac_bonus: optional - A bonus added to the combatant’s armor class while this effect is active.

max_hp_value: optional - A value to set the combatant’s maximum hit points to while this effect is active.

Note

If both max_hp_value and max_hp_bonus are specified, the resulting value will be equal to max_hp_value + max_hp_bonus.

If multiple effects specify max_hp_value, the highest value will be used.

max_hp_bonus: optional - A bonus added to the combatant’s maximum hit points while this effect is active.

save_bonus: optional - A bonus that this effect grants to all of the combatant’s saving throws.

save_adv: optional - A list of stat names (e.g. strength) that the combatant should have advantage on for their respective saving throws while this effect is active. Use all as a stat name to specify all stats.

save_dis: optional - A list of stat names (e.g. strength) that the combatant should have disadvantage on for their respective saving throws while this effect is active. Use all as a stat name to specify all stats.

check_bonus: optional - A bonus that this effect grants to all of the combatant’s skill checks.

check_adv: optional - A list of skill names (e.g. sleightOfHand, strength) that the combatant should have advantage on for ability checks for while this effect is active. If a base ability is given, the advantage will apply to all skills based on that ability (e.g. strength gives advantage on athletics checks). Use all as a stat name to specify all skills.

check_dis: optional - A list of skill names (e.g. sleightOfHand, strength) that the combatant should have disadvantage on for ability checks for while this effect is active. If a base ability is given, the disadvantage will apply to all skills based on that ability (e.g. strength gives disadvantage on athletics checks). Use all as a stat name to specify all skills.

AttackInteraction

{
    attack: Attack;
    defaultDC?: IntExpression;
    defaultAttackBonus?: IntExpression;
    defaultCastingMod?: IntExpression;
}

Used to specify an attack granted by an initiative effect: some automation that appears in the combatant’s !action list and can be run with a command.

class AttackInteraction

attack

The Attack model is any valid individual entity as exported by the attack editor on the Avrae Dashboard:

{
    _v: 2;
    name: string;
    automation: Effect[];
    verb?: string;
    proper?: boolean;
    criton?: number;
    phrase?: string;
    thumb?: string;
    extra_crit_damage?: string;
}

defaultDC: optional - The default saving throw DC to use when running the automation. If not provided, defaults to the targeted combatant’s default spellcasting DC (or any DC specified in the automation). Use this if the effect’s DC depends on the original caster’s DC, rather than the target’s DC.

defaultAttackBonus: optional - The default attack bonus to use when running the automation. If not provided, defaults to the targeted combatant’s default attack bonus (or any attack bonus specified in the automation). Use this if the effect’s attack bonus depends on the original caster’s attack bonus, rather than the target’s attack bonus.

defaultCastingMod: optional - The default spellcasting modifier to use when running the automation. If not provided, defaults to the targeted combatant’s default spellcasting modifier. Use this if the effect’s spellcasting modifier depends on the original caster’s spellcasting modifier, rather than the target’s spellcasting modifier.

ButtonInteraction

{
    automation: Effect[];
    label: AnnotatedString;
    verb?: AnnotatedString;
    style?: IntExpression;
    defaultDC?: IntExpression;
    defaultAttackBonus?: IntExpression;
    defaultCastingMod?: IntExpression;
}

Used to specify a button that will appear on the targeted combatant’s turn and execute some automation when pressed.

Note

Any initiative effects applying an offensive effect to the caster will not be considered when a ButtonInteraction is run, to prevent scenarios where an effect granting a damage bonus to the caster increases the damage done by a damage over time effect and other similar scenarios.

You may think of this as a ButtonInteraction’s caster being a temporary actor without any active initiative effects.

class ButtonInteraction

automation: The automation to run when this button is pressed.

label: The label displayed on the button.

verb: optional, default “uses {label}” - The verb to use for the displayed output when the button is pressed (e.g. “is on fire” would display “NAME is on fire!”).

style: optional, default blurple - The color of the button (1 = blurple, 2 = grey, 3 = green, 4 = red).

defaultDC: optional - The default saving throw DC to use when running the automation. If not provided, defaults to the targeted combatant’s default spellcasting DC (or any DC specified in the automation). Use this if the effect’s DC depends on the original caster’s DC, rather than the target’s DC.

defaultAttackBonus: optional - The default attack bonus to use when running the automation. If not provided, defaults to the targeted combatant’s default attack bonus (or any attack bonus specified in the automation). Use this if the effect’s attack bonus depends on the original caster’s attack bonus, rather than the target’s attack bonus.

defaultCastingMod: optional - The default spellcasting modifier to use when running the automation. If not provided, defaults to the targeted combatant’s default spellcasting modifier. Use this if the effect’s spellcasting modifier depends on the original caster’s spellcasting modifier, rather than the target’s spellcasting modifier.

Remove IEffect

New in version 4.0.0.

{
    type: "remove_ieffect";
    removeParent?: "always" | "if_no_children";
}

Removes the initiative effect that triggered this automation. Only works when run in execution triggered by an initiative effect, such as a ButtonInteraction (see ButtonInteraction).

class RemoveIEffect

removeParent

optional, default null - If the removed effect has a parent, whether to remove the parent.

null (default) - Do not remove the parent effect.
"always" - If the removed effect has a parent, remove it too.
"if_no_children" - If the removed effect has a parent and its only remaining child was the removed effect, remove it too.

Variables

No variables are exposed.

Roll

{
    type: "roll";
    dice: AnnotatedString;
    name: string;
    higher?: {int: string};
    cantripScale?: boolean;
    hidden?: boolean;
}

Rolls some dice and saves the result in a variable. Displays the roll and its name in a Meta field, unless hidden is true.

class Roll

dice: An AnnotatedString detailing what dice to roll.

name: The variable name to save the result as.

higher: optional - How much to add to the roll when a spell is cast at a certain level.

cantripScale: optional - Whether this roll should scale like a cantrip.

hidden: optional - If true, won’t display the roll in the Meta field, or apply any bonuses from the -d argument.

Variables

(supplied name) (RollEffectMetaVar) The result of the roll.
- You can use this in an AnnotatedString to retrieve the simplified result of the roll. Using this variable in an AnnotatedString will always return a string that itself can be rolled.
- You can use this in an IntExpression to retrieve the roll total.
- You can compare this variable against a number to determine if the total of the roll equals that number.
lastRoll (int) The integer total of the roll.

Text

{
    type: "text";
    text: AnnotatedString | AbilityReference;
}

Outputs a short amount of text in the resulting embed.

class Text

text

Either:

An AnnotatedString (the text to display).
An AbilityReference (see AbilityReference). Displays the ability’s description in whole.

Set Variable

New in version 2.7.0.

{
    type: "variable";
    name: string;
    value: IntExpression;
    higher?: {int: IntExpression};
    onError?: IntExpression;
}

Saves the result of an IntExpression to a variable without displaying anything.

class SetVariable

name: The name of the variable to save.

value: The value to set the variable to.

higher: optional - What to set the variable to instead when a spell is cast at a higher level.

onError: optional - If provided, what to set the variable to if the normal value would throw an error.

Condition (Branch)

New in version 2.7.0.

{
    type: "condition";
    condition: IntExpression;
    onTrue: Effect[];
    onFalse: Effect[];
    errorBehaviour?: "true" | "false" | "both" | "neither" | "raise";
}

Run certain effects if a certain condition is met, or other effects otherwise. AKA “branch” or “if-else”.

class Condition

condition: The condition to check.

onTrue: The effects to run if condition is True or any non-zero value.

onFalse: The effects to run if condition is False or 0.

errorBehaviour

How to behave if the condition raises an error:

"true": Run the onTrue effects.
"false": Run the onFalse effects. (default)
"both": Run both the onTrue and onFalse effects, in that order.
"neither": Skip this effect.
"raise": Raise the error and halt execution.

Use Counter

New in version 2.10.0.

{
    type: "counter";
    counter: string | SpellSlotReference | AbilityReference;
    amount: IntExpression;
    allowOverflow?: boolean;
    errorBehaviour?: null | "warn" | "raise";
}

Uses a number of charges of the given counter, and displays the remaining amount and delta.

Note

Regardless of the current target, this effect will always use the caster’s counter/spell slots!

class UseCounter

counter: The name of the counter to use (case-sensitive, full match only), or a reference to a spell slot (see SpellSlotReference).

amount: The number of charges to use. If negative, will add charges instead of using them.

allowOverflow: optional, default False - If False, attempting to overflow/underflow a counter (i.e. use more charges than available or add charges exceeding max) will error instead of clipping to bounds.

errorBehaviour

optional, default “warn” - How to behave if modifying the counter raises an error:

null: All errors are silently consumed.
"warn": Automation will continue to run, and any errors will appear in the output. (default)
"raise": Raise the error and halt execution.

Some, but not all, possible error conditions are:

The target does not have counters (e.g. they are a monster)
The counter does not exist
allowOverflow is false and the new value is out of bounds

Variables

lastCounterName (str) The name of the last used counter. If it was a spell slot, the level of the slot (safe to cast to int, i.e. int(lastCounterName)). (None on error).
lastCounterRemaining (int) The remaining charges of the last used counter (0 on error).
lastCounterUsedAmount (int) The amount of the counter successfully used.
lastCounterRequestedAmount (int) The amount of the counter requested to be used (i.e. the amount specified by automation or requested by -amt, regardless of the presence of the -i arg).

SpellSlotReference

{
    slot: number | IntExpression;
}

class SpellSlotReference

slot: The level of the spell slot to reference ([1..9]).

AbilityReference

{
    id: number;
    typeId: number;
}

In most cases, an AbilityReference should not be constructed manually; use the Automation editor to select an ability instead. A list of valid abilities can be retrieved from the API at /gamedata/limiteduse.

Note

The Automation Engine will make a best effort at discovering the appropriate counter to use for the given ability - in most cases this won’t affect the chosen counter, but in some cases, it may lead to some unexpected behaviour. Some examples of counter discovery include:

Choosing Channel Divinity (Paladin) may discover a counter granted by the Cleric’s Channel Divinity feature
Choosing Breath Weapon (Gold) may discover a counter for a breath weapon of a different color
Choosing Sorcery Points (Sorcerer) may discover a counter granted by the Metamagic Adept feat

class AbilityReference

id: The ID of the ability referenced.

typeId: The DDB entity type ID of the ability referenced.

Cast Spell

New in version 2.11.0.

{
    type: "spell";
    id: int;
    level?: int;
    dc?: IntExpression;
    attackBonus?: IntExpression;
    castingMod?: IntExpression;
}

Executes the given spell’s automation as if it were immediately cast. Does not use a spell slot to cast the spell. Can only be used at the root of automation. Cannot be used inside a spell’s automation.

This is usually used in features that cast spells using alternate resources (i.e. Use Counter, Cast Spell).

class CastSpell

id: The DDB entity id of the spell to cast. Use the Automation Editor to select a spell or the /gamedata/spells API endpoint to retrieve a list of valid spell IDs.

level: optional - The (slot) level to cast the spell at.

dc: optional - The saving throw DC to use when casting the spell. If not provided, defaults to the caster’s default spellcasting DC (or any DC specified in the spell automation).

attackBonus: optional - The spell attack bonus to use when casting the spell. If not provided, defaults to the caster’s default spell attack bonus (or any attack bonus specified in the spell automation).

castingMod: optional - The spellcasting modifier to use when casting the spell. If not provided, defaults to the caster’s default spellcasting modifier.

Variables

No variables are exposed.

Ability Check

New in version 4.0.0.

{
    type: "check";
    ability: string | string[];
    contestAbility?: string | string[];
    dc?: IntExpression;
    success?: Effect[];
    fail?: Effect[];
    contestTie?: "fail" | "success" | "neither";
    adv?: -1 | 0 | 1;
}

An Ability Check effect forces a targeted creature to make an ability check, optionally as a contest against the caster. It must be inside a Target effect.

class Check

ability

The ability to make a check for. Must be one of or a list of the following:

"acrobatics"
"animalHandling"
"arcana"
"athletics"
"deception"
"history"
"initiative"
"insight"
"intimidation"
"investigation"
"medicine"
"nature"
"perception"
"performance"
"persuasion"
"religion"
"sleightOfHand"
"stealth"
"survival"
"strength"
"dexterity"
"constitution"
"intelligence"
"wisdom"
"charisma"

If multiple skills are specified, uses the highest modifier of all the specified skills.

contestAbility

optional - Which ability of the caster’s to make a contest against. Must be one of or a list of the valid skills listed above. If multiple skills are specified, uses the highest modifier of all the specified skills.

Mutually exclusive with dc.

dc

optional - An IntExpression that specifies the check’s DC. If neither dc nor contestAbility is given, the check will not run either the fail or success nodes.

Mutually exclusive with contestAbility.

success: optional - A list of effects to execute on a successful check or if the target wins the contest. Requires the contestAbility or dc attribute to be set.

fail: optional - A list of effects to execute on a failed check or if the target loses the contest. Requires the contestAbility or dc attribute to be set.

contestTie: optional, default success - Which list of effects to run if the ability contest results in a tie.

adv: optional, default 0 - Whether the check should have advantage by default (-1 = disadvantage, 1 = advantage, 0 = no advantage).

Variables

lastCheckRollTotal (int) The result of the last check roll (0 if no roll was made).
lastCheckNaturalRoll (int) The natural roll of the last check roll (e.g. 10 in 1d20 (10) + 5 = 15; 0 if no roll was made).
lastCheckAbility (str) The title-case full name of the rolled skill (e.g. "Animal Handling", "Arcana").
lastCheckDidPass (bool or None) If a DC was given, whether the target succeeded the check. If a contest was specified, whether the target won the contest. None if no or contest given.
lastCheckDC (int or None) If a DC was given, the DC of the last save roll. None if no DC given.

Contest Variables

lastContestRollTotal (int or None) The result of the caster’s contest roll; None if no contest was made.
lastContestNaturalRoll (int or None) The natural roll of the caster’s contest roll (e.g. 10 in 1d20 (10) + 5 = 15; None if no contest was made).
lastContestAbility (str or None) The title-case full name of the skill the caster rolled (e.g. "Animal Handling", "Arcana"). None if no contest was made.
lastContestDidTie (bool) Whether a ability contest resulted in a tie.

AnnotatedString

An AnnotatedString is a string that can access saved variables. To access a variable, surround the name in brackets (e.g. {damage}). Available variables include:

implicit variables from Effects (see relevant effect for a list of variables it provides)
any defined in a Roll or Set Variable effect
all variables from the Cvar Table

This will replace the bracketed portion with the value of the meta variable.

To perform math inside an AnnotatedString, surround the formula with two curly braces (e.g. {{floor(dexterityMod+spell)}}).

IntExpression

An IntExpression is similar to an AnnotatedString in its ability to use variables and functions. However, it has the following differences:

Curly braces around the expression are not required
An IntExpression can only contain one expression
The result of an IntExpression must be an integer.

These are valid IntExpressions:

8 + proficiencyBonus + dexterityMod
12
floor(level / 2)

These are not valid IntExpressions:

1d8
DC {8 + proficiencyBonus + dexterityMod}

Examples

Attack

A normal attack:

[
  {
    "type": "target",
    "target": "each",
    "effects": [
      {
        "type": "attack",
        "attackBonus": "dexterityMod + proficiencyBonus",
        "hit": [
          {
            "type": "damage",
            "damage": "1d10[piercing]"
          }
        ],
        "miss": []
      }
    ]
  }
]

Save

A spell that requires a Dexterity save for half damage:

[
  {
    "type": "roll",
    "dice": "8d6[fire]",
    "name": "damage",
    "higher": {
      "4": "1d6[fire]",
      "5": "2d6[fire]",
      "6": "3d6[fire]",
      "7": "4d6[fire]",
      "8": "5d6[fire]",
      "9": "6d6[fire]"
    }
  },
  {
    "type": "target",
    "target": "all",
    "effects": [
      {
        "type": "save",
        "stat": "dex",
        "fail": [
          {
            "type": "damage",
            "damage": "{damage}"
          }
        ],
        "success": [
          {
            "type": "damage",
            "damage": "({damage})/2"
          }
        ]
      }
    ]
  },
  {
    "type": "text",
    "text": "Each creature in a 20-foot radius must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one."
  }
]

Attack & Save

An attack from a poisoned blade:

[
  {
    "type": "target",
    "target": "each",
    "effects": [
      {
        "type": "attack",
        "attackBonus": "strengthMod + proficiencyBonus",
        "hit": [
          {
            "type": "damage",
            "damage": "1d10[piercing]"
          },
          {
            "type": "save",
            "stat": "con",
            "dc": "12",
            "fail": [
              {
                "type": "damage",
                "damage": "1d6[poison]"
              }
            ],
            "success": []
          }
        ],
        "miss": []
      }
    ]
  },
  {
    "type": "text",
    "text": "On a hit, a target must make a DC 12 Constitution saving throw or take 1d6 poison damage."
  }
]

Draining Attack

An attack that heals the caster for half the amount of damage dealt:

[
  {
    "type": "variable",
    "name": "lastDamage",
    "value": "0"
  },
  {
    "type": "target",
    "target": "each",
    "effects": [
      {
        "type": "attack",
        "attackBonus": "charismaMod + proficiencyBonus",
        "hit": [
          {
            "type": "damage",
            "damage": "3d6[necrotic]"
          }
        ],
        "miss": []
      }
    ]
  },
  {
    "type": "target",
    "target": "self",
    "effects": [
      {
        "type": "damage",
        "damage": "-{lastDamage}/2 [heal]"
      }
    ]
  },
  {
    "type": "text",
    "text": "On a hit, the target takes 3d6 necrotic damage, and you regain hit points equal to half the amount of necrotic damage dealt."
  }
]

Target Health-Based

A spell that does different amounts of damage based on whether or not the target is damaged:

[
  {
    "type": "target",
    "target": "each",
    "effects": [
      {
        "type": "save",
        "stat": "wis",
        "fail": [
          {
            "type": "condition",
            "condition": "target.hp < target.max_hp",
            "onTrue": [
              {
                "type": "damage",
                "damage": "1d8 [necrotic]"
              }
            ],
            "onFalse": [
              {
                "type": "damage",
                "damage": "1d4 [necrotic]"
              }
            ],
            "errorBehaviour": "both"
          }
        ],
        "success": []
      }
    ]
  },
  {
    "type": "text",
    "text": "The target must succeed on a Wisdom saving throw or take 1d4 necrotic damage. If the target is missing any of its hit points, it instead takes 1d8 necrotic damage."
  }
]

Area Vampiric Drain

An effect that heals the caster for the total damage dealt to all targets:

[
  {
    "type": "variable",
    "name": "totalDamage",
    "value": "0"
  },
  {
    "type": "target",
    "target": "each",
    "effects": [
      {
        "type": "damage",
        "damage": "1d6 [necrotic]"
      },
      {
        "type": "variable",
        "name": "totalDamage",
        "value": "totalDamage + lastDamage"
      }
    ]
  },
  {
    "type": "target",
    "target": "self",
    "effects": [
      {
        "type": "damage",
        "damage": "-{totalDamage} [heal]"
      }
    ]
  },
  {
    "type": "text",
    "text": "Each creature within 10 feet of you takes 1d6 necrotic damage. You regain hit points equal to the sum of the necrotic damage dealt."
  }
]

Damage Over Time Effect

An effect that lights the target on fire, adding two buttons on their turn to take the fire damage and douse themselves.

[
  {
    "type": "target",
    "target": "each",
    "effects": [
      {
        "type": "ieffect2",
        "name": "Burning",
        "buttons": [
          {
            "label": "Burning",
            "verb": "is on fire",
            "style": "4",
            "automation": [
              {
                "type": "target",
                "target": "self",
                "effects": [
                  {
                    "type": "damage",
                    "damage": "1d6 [fire]"
                  }
                ]
              },
              {
                "type": "text",
                "text": "At the start of each of the target's turns, the target takes 1d6 fire damage."
              }
            ]
          },
          {
            "label": "Douse",
            "verb": "puts themself out",
            "automation": [
              {
                "type": "remove_ieffect"
              },
              {
                "type": "text",
                "text": "The target can use an action to put themselves out."
              }
            ]
          }
        ]
      }
    ]
  }
]