Number Providers (number_provider_type)

Any number that has to change with level, realm or event context is a number provider. It accepts three input forms: a JSON number, an expression string, and an object with a type.

Evaluation happens entirely on the server; the client only sees the synchronized result. The same definition can produce different numbers on different entities, because the variables are read from the entity at the moment of evaluation.

Form	Written as	Equivalent to
Number	5	mxt:constant
String	"4 + level * 0.5"	mxt:expression
Object	{"type": "mxt:uniform", "min": 1, "max": 3}	That type's own shape

In the object form, type sits next to the other keys; there is no outer wrapper.

"amount": 5

"amount": "4 + level * 0.5"

"amount": {"type": "mxt:constant", "value": 5}

Expression Strings

A string is always an expression: operators, parentheses, functions, and the variable names the context provides. The load checks three things — whether the expression parses, whether every name in params is a legal variable name, and whether every key in params really appears in the expression. Any one of them failing is a decode error: the definition does not load, but the loader collects every failing entry of that load and lists them together, rather than reporting only the first.

A string is shorthand for mxt:expression; writing a type inside the string is neither needed nor accepted.

{
  "type": "mxt:expression",
  "expression": "base_damage * multiplier",
  "params": {
    "base_damage": 8,
    "multiplier": "1 + level * 0.1"
  }
}

The values in params are number providers themselves and accept all three forms. During evaluation, params overrides the variable of the same name.

Whether a variable name is legal is decided at load time: the first character is a letter or an underscore, the rest may be letters, digits or underscores. A key in params that the expression never uses is a load error too, rather than something kept around unused.

Whether a name is available is decided by the built-in variable table together with the current context, and that is only known at evaluation time. A name the context cannot supply is reported: a development environment prints the full ERROR log (with the exception and stack trace), production prints one WARN line per distinct message; both keep evaluating with 0 and never abort the caller. A result that is not finite is reported the same way and returns 0. The name list is in Formula Variables.

Built-In Number Providers

Each type below gets its own third-level heading. A field that is not marked required in its table may be omitted.

mxt:constant

A single fixed number. The JSON number shorthand is equivalent to it.

Field	Type	Default	Description
value	Double	required	Fixed number; must be finite

{"type": "mxt:constant", "value": 12}

mxt:expression

An exp4j expression; params may override context variables.

Field	Type	Default	Description
expression	String	required	The expression text
params	Map of variable name to number provider	{}	Overrides context variables of the same name

{
  "type": "mxt:expression",
  "expression": "heal + bonus",
  "params": {"bonus": "level * 0.5"}
}

mxt:context_variable

Reads one context variable directly, falling back when it cannot be read.

Field	Type	Default	Description
variable	String	required	Variable name; must not be blank
fallback	Double	0	Value returned when the built-in variable table does not know the name at all; must be finite

fallback only covers "nothing recognizes this name". A name that is known but this context cannot supply still takes the error-reporting path and returns 0, the same as an expression.

{"type": "mxt:context_variable", "variable": "absorbed_aura", "fallback": 0}

mxt:sum

Adds several terms together.

Field	Type	Default	Description
summands	List of number providers	required	At least one entry; an empty list is rejected at load time

{"type": "mxt:sum", "summands": [1, "level * 0.25", {"type": "mxt:uniform", "min": 0, "max": 2}]}

mxt:uniform

Draws a uniform random value inside a range.

Field	Type	Default	Description
min	Number provider	required	Lower bound
max	Number provider	required	Upper bound

Both bounds are evaluated first, and the random source comes from the evaluation context. When min is greater than max, or either bound is NaN, the provider logs a warning and returns 0; when the two are equal it returns that value directly without rolling.

{"type": "mxt:uniform", "min": 2, "max": "2 + level"}

mxt:binomial

n Bernoulli trials; returns the number of successes.

Field	Type	Default	Description
n	Number provider	required	Number of trials; after evaluation it must be an integer in 0..16384
p	Number provider	required	Probability of one success; after evaluation it must be in 0..1

When n is not an integer or is out of range, or p is out of range (including evaluating to NaN), the provider logs a warning and returns 0.

{"type": "mxt:binomial", "n": 5, "p": 0.35}

mxt:weighted_list

Picks one entry by weight and evaluates it.

Field	Type	Default	Description
distribution	List of entries	required	At least one entry; an empty list is rejected at load time

Each entry is a weighted entry, with the same shape everywhere in the mod:

Field	Type	Default	Description
value	Number provider	required	Value returned when this entry is picked
weight	Integer	1	Integer weight

An entry with a weight of ≤ 0 counts as 0 and is never picked. When every weight in the table is 0 (or the weights sum overflows the integer range), the provider logs a warning and returns 0 without drawing any entry.

{
  "type": "mxt:weighted_list",
  "distribution": [
    {"value": 1, "weight": 3},
    {"value": "level * 2", "weight": 1}
  ]
}

mxt:conditional

Checks the branches in order and returns the value of the first branch whose condition passes.

Field	Type	Default	Description
branches	List of branches	[]	Checked in written order
fallback	Number or expression string	none	Value returned when no player is available or no branch matches; returns 0 when omitted

Each branch is:

Field	Type	Default	Description
condition	Entity condition	required	Condition tested against the player
value	Number provider	required	Value returned when the condition passes

fallback accepts only a number or an expression string; writing an object such as {"type": "mxt:constant", "value": 1} is a load error.

{
  "type": "mxt:conditional",
  "branches": [
    {"condition": {"type": "mxt:sneaking"}, "value": 4},
    {"condition": {"type": "mxt:has_realm", "aura": "example:qi"}, "value": "level + 1"}
  ],
  "fallback": 1
}

mxt:js

Hands this one evaluation to a server-side script.

Field	Type	Default	Description
id	String	required	Callback ID registered with MxtValues.number(...)
params	Object	{}	Arbitrary JSON passed to the callback

The callback receives the same formula context the built-in types receive; how to read it is in MxtValues. When no callback is registered for id, the provider logs a warning and returns 0 — it does not fail the load.

{"type": "mxt:js", "id": "example:luck_roll", "params": {"base": 3}}

Aura Concentration Sources

Two numbers describe how much aura a position holds. They are not in mxt:number_provider_type but in the resource value provider registry resource_value_provider_type:

type	Description
mxt:environment_concentration	The environmental template concentration at the current position. Only environmental sources such as biome, dimension and zone are counted; chunk storage and the aura released by blocks and formations are not.
mxt:actual_concentration	The final resolved concentration at the current position, including the environment, chunk storage and every active source such as blocks and formations.

Both read world state and therefore need a position: with no entity to attach to, they resolve to 0. The full list of resource value providers is in Resource Value Providers.