Smelt’s MCC Syntax


There are 5 different triggers used in the Smelt MCC syntax. A trigger is used to specify what will be in the following lines.

  1. The hash # triggers a new command block row.
    Used to create a new row of command blocks. Text after the # is used to label the row.
  2. The right angle bracket > trigger is for JSON properties.
    A valid JSON string (in curly {} brackets) is then used to set properties for the commands.
  3. The dollar $ is used to define variables.
  4. The / slash is used to write Minecraft commands.
  5. The exclamation ! trigger is used to execute Smelt’s bang commands.

Let’s consider each of these one at a time:

# New command block row

Each of these starts a new row of command blocks.

Any text found after the initial “#” is used to generate a “row marker” (a hidden marker entity with the text as the CustomName).

This helps to recognise rows of command blocks in your Minecraft map.

A line with no text after the “#” can be used to create a gap between your command block rows. No row marker will be created.

> JSON properties

After the > character, the rest of the content should be valid JSON using curly brackets {}.

For example >{"type":"repeating","auto":true}.

This is used to set the properties of all command blocks following until a tag is changed.

Properties available to use are:


This defines the type of command block that will be used for the following commands.

Possible values are; "impulse", "repeating", "chain", "impulse-chain" or "repeating-chain".

Example: >{"type":"repeating"}

Note: The impulse-chain and repeating-chain types will result in the first command block being either an impulse or repeating type (respectively) and then all other command blocks after that will be chain command blocks until a new type is specified. The following chain command blocks will be “Always active” regardless of the auto setting last used (explained below).


This defines whether the following command blocks with be “Always active” (true), or “Require redstone” (false). This can be overridden in chain command blocks when a type value of the impulse-chain or repeating-chain is used (as explained above).

Possible values are true or false. Double quotes should not be used around values on this property.

Example: >{"auto":false}


This defines whether the following command blocks will be “Conditional”, meaning that they will only execute if the previous command block executes successfully.

Possible values are true or false. Double quotes should not be used around values on this property.

Example: >{"conditional":true}


This defined whether the “TrackOutput” feature will be turned on or off on following command blocks.

Possible values are true or false. Double quotes should not be used around values on this property.

When used in an module, this will override the Commands.DefaultTrackOutput configuration setting for that module.

Example: >{"trackOutput":true}


This defines the executing entity for all following command blocks.

Currently this only supports one entity selector, but it may be extended to allow for more as a list.

Any valid entity selector, e.g. >{"executeAs":"@a[score_lives=0]"}

This will be inserted before any following commands as /execute @a[score_lives=0] ~ ~ ~ /say Hello World.

Use >{"executeAs":""} to reset this option.


This is used to define a ‘marker’ entity (either an ArmorStand or AreaEffectCloud according to the config) to be summoned at the same location as each command block to follow. Each marker entity will have the tag provided as the value of markerTag.

This can be useful for targeting a specific command block, or for setting up a random option system.

Possible values are any string that can be used as a scoreboard tag. e.g. >{"markerTag":"randomPowerup"}.

Use >{"markerTag":""} to reset this option and stop entities from being summoned in coming command blocks.

Example use case:

>{"type":"impulse", "auto":false, "conditional":false}
    /scoreboard players set @e[name=SYSTEM] power_up_option 1
    /scoreboard players set @e[name=SYSTEM] power_up_option 2
    /scoreboard players set @e[name=SYSTEM] power_up_option 3
    /scoreboard players set @e[name=SYSTEM] power_up_option 4
    /scoreboard players set @e[name=SYSTEM] power_up_option 5
    /scoreboard players set @e[name=SYSTEM] power_up_option 6

!event CyclePowerups
    >{"type":"chain", "conditional":false}
    /execute @e[tag=randomPowerUp] ~ ~ ~ blockdata ~ ~ ~ {auto:0b}
    /execute @r[tag=randomPowerUp] ~ ~ ~ blockdata ~ ~ ~ {auto:1b}


There are a number of properties used to change the layout of a module, as showing in this example:

    "moduleStartX": 0,
    "moduleStartY": 0,
    "moduleStartZ": 0,
    "moduleStopX": 15,
    "moduleStopY": 15,
    "moduleStopZ": 15,
    "moduleBorder": 1

The moduleStart and moduleStop properties are used to specify the starting and stopping coordinates (X, Y and Z) of the module, relative to the source command block. This effectively allows you to change the size and location of each module.

The moduleBorder property is used to change the border of empty blocks that surrounds the module, allowing space to stop modules touching and for display markers. This border only applies on the x and z axis, not on the y axis. When the “start” coordinates are 0, this border should be at least 1.

For example, the settings below will produce the same output as above by reducing the border but changing the start and stop coordinates:

    "moduleStartX": 1,
    "moduleStartY": 1,
    "moduleStartZ": 1,
    "moduleStopX": 14,
    "moduleStopY": 14,
    "moduleStopZ": 14,
    "moduleBorder": 0

$ Variables

Variables can be declared, one per line, like so:


Then variables can use used in other commands with either the $VARIABLE_NAME or ${VARIABLE_NAME} syntax.

/say Hello ${name}! Good to see you.

Output: [@] Hello Gnasp! Good to see you.

You can even add variables values to other definitions:

$nameAndTitle=Mr $name

/say Good day ${nameAndTitle}!

Output: [@] Good day Mr Gnasp!

Note: The syntax without brackets can only be used with the variable is not being used as part of a word. For example: /say $nameIsCool will not work for the $name variable, using /say ${name}IsCool will work.

/ Minecraft commands

Each of these commands is converted into the game, and the command-blocks executing them will use the properties from any previous JSON properties.

You can use anything on these that can be put into a command block in the game.

! Bang commands

These are used to call custom commands built into Smelt or available via plugins.

A bang command will in turn generate standard Minecraft commands to be imported into your map.

See Docs/BangCommands and Docs/Plugins for more information.

Wrapping Lines

Sometimes you might want a command to wrap to the next line because it’s just too long. Smelt now automatically expects this. Unless a trigger character is found at the beginning of a line, Smelt will consider each line to be a continuation of the last line.


/say I've got something really lengthy to say. 
It's going to take a while. 
It might not squeeze onto one line.

Output: [@] I've got something really lengthy to say. It's going to take a while. It might not squeeze onto one line.

Each concatenated line will be added to the last with an additional space included.



# repeatThing
/testfor @e[name=repeatThing]
    /say repeatThing exists!
        >{"type":"chain", "conditional":false}
        /say Hi $name!
        /say repeatThing finised!
# Another row
/say TEST
    >{"type":"chain", "auto":true}
    /say TEST 2
    /say TEST 3

This will create the following command-blocks: