Bi-entity Action Types

A bi-entity action operates on a pair of entities: an actor and a target. The pair is supplied by whatever data table declares the action, so the action itself only describes what to do with the two entities it is given.

Bi-entity actions are a Java (built-in) registry, so their type ids are fixed and a data pack cannot add new ones. type selects the built-in type and its value is one of the ids tabulated on this page, written with the mxt namespace. A data pack never adds or removes entries in this registry. Only Java code or the KubeJS bridge can introduce custom action types — see the KubeJS API.

In the tables below, a field name followed by ? is optional; every other listed field must be present. The Fields column lists the JSON keys taken directly from the type's codec.

Common Structure

An action is a JSON object whose type field names the built-in type. All remaining keys are the fields declared by that type.

{
  "type": "mxt:damage_target",
  "amount": 4
}

Because actions are used as values inside other data tables, the same structure usually appears nested under a field such as bientity_action:

"bientity_action": {
  "type": "mxt:actor_action",
  "action": {
    "type": "mxt:heal",
    "amount": 2
  }
}

The nested action of mxt:actor_action is an entity action, so it takes entity action ids; a bi-entity action id such as mxt:heal_target would be wrong in that position.

Anywhere a bi-entity action is expected, an array of actions is also accepted. The array is shorthand for mxt:sequence and runs its entries in order:

"bientity_action": [
  { "type": "mxt:mount" },
  { "type": "mxt:heal_target", "amount": 1 }
]

Field Types Are Shared

Fields that take a numeric value generally accept a number provider instead of a fixed number, so formulas and random values work everywhere a plain number does.

Datapack Visual Editor

The Datapack Visual Editor shows the field list of every type interactively, which is handy for checking a field name without reading the tables here.

Meta Types

Meta actions control whether, how often and in what order other bi-entity actions run. They are the actions that take other actions as fields.

Type	Fields	Description
mxt:no_op	—	Does nothing; this is the default action for optional action fields.
mxt:js	id, params?	Calls a bi-entity action handler that was registered through the KubeJS bridge.
mxt:sequence	actions	Runs a list of bi-entity actions in order.
mxt:chance	action, chance, fail_action?	Runs action with probability chance, otherwise runs fail_action.
mxt:if_else	condition, if_action, else_action?	Runs if_action when the bi-entity condition passes, otherwise else_action.
mxt:choice	actions	Picks one entry from a weighted list and runs it.

Each entry of a choice list is a weighted wrapper around a nested action:

Entry Field	Type	Default	Description
element	Bi-entity action	required	The action this entry runs when it is picked.
weight	Integer	1	Relative weight; larger weights are picked more often.

Action Types

Type	Fields	Description
mxt:mount	—	Makes the actor start riding the target.
mxt:damage_target	amount	Damages the target, crediting the actor as the attacker so kill credit and aggro follow them; both layers of the damage pipeline apply.
mxt:heal_target	amount	Heals the target.
mxt:transfer_resource	resource, amount	Moves a resource amount from the actor to the target, clamped so values never become negative or exceed the target's maximum.
mxt:add_velocity	x?, y?, z?, reference?, client?, server?, set?	Adds velocity to the target, or sets it when set is true; reference chooses the frame the vector is expressed in.
mxt:teleport	teleport_actor?, teleport_target?, rotate?	Moves either endpoint to the other endpoint's position: the target is moved to the actor by default, and the actor is moved to the target when teleport_actor is true.
mxt:actor_action	action	Applies an entity action to the actor.
mxt:target_action	action	Applies an entity action to the target.

Nested Values

mxt:if_else takes a bi-entity condition, and mxt:actor_action / mxt:target_action take entity actions.

The reference field is specific to this action and accepts position (the default, resolving the vector in the direction from the actor to the target) or rotation (resolving it from the actor's view direction).