MxtCosts and MxtResources

MxtCosts

Method	Parameters	Return value	Description
check(player, definition)	Player, one Cost JSON	boolean	Only checks; does not change the inventory or resources. It is read-only, so a client script may call it.
consume(player, definition)	Player, one Cost JSON	boolean	Checks first and then pays; when it cannot be paid nothing is changed. Server-only: on a client script it logs one warning and returns false without touching the player.
register(id, check, consume)	Callback ID, (player, params, context) => boolean, (player, params, context) => void	void	Registers a script cost. Datapack type: mxt:js.

MxtCosts.register('example:quest_token',
  (player, params, context) => {
    const needed = params.count || 1
    return player.persistentData.getInt('tokens') >= needed
  },
  (player, params, context) => {
    const needed = params.count || 1
    player.persistentData.putInt('tokens', player.persistentData.getInt('tokens') - needed)
  }
)

{"type": "mxt:js", "id": "example:quest_token", "params": {"count": 3}}

A script cost needs a player, because a cost that is not a resource cost makes the whole ability require one. Cost is checked with a player alone, so the context a cost callback receives is built from that player and carries no event payload; context.value('level') works, context.value('damage') does not.

Full cost registry dispatch is supported. The current built-in types:

// Consume a resource. Typed cost form.
{ type: 'mxt:resource', resource: 'mxt:spirit_power', amount: 10 }

// Consume a resource. The id shorthand, which is also the resource-cost form MxtResources.consume takes.
{ id: 'mxt:spirit_power', amount: 10 }

// Consume items. items accepts an item ID, an item tag, or an ItemMatcher object.
{ type: 'mxt:item', items: ['minecraft:emerald', '#c:mystic_gems'], amount: 2 }

A single Cost is the safe entry point; for several resources use MxtResources.consume below, which has atomic transaction semantics. Do not treat several MxtCosts.consume calls as one atomic payment.

MxtResources

Method	Parameters	Return value	Description
consume(entity, costs)	Entity, ResourceCost[]	ResourceTransactions.Result	Pays a group of resources atomically; when any one of them is insufficient, none of the group is deducted.

Each element of costs is a resource cost, whose fields are id and amount:

const result = MxtResources.consume(player, [
  { id: 'mxt:spirit_power', amount: 10 },
  { id: 'mxt:fire_aura', amount: 'level + 2' }
])

if (result.committed()) {
  console.info(`Deducted: ${result.amounts()}`)
} else {
  console.warn(`Insufficient resource: ${result.failedResource()}`)
}

The accessors of the returned record are committed(), failedResource() and amounts(). On the client, with an invalid formula, or when the resources are not satisfied, committed() is false.