Your commands from Discord

How it reaches your addon

The owner allows a command by name on the world's Commands tab, and then anyone allowed can type it in Discord:

/relay run command: myaddon:option 12

BedrockRelay runs it in the world the way any script does, with Dimension.runCommand(). Your command can't tell it came from Discord. It's the same on dedicated servers and Realms, with cheats on or off. The owner can also run commands from the console on the dashboard, which works the same way.

Permission level

Scripts run commands at the GameDirectors level, so the permissionLevel you register with decides whether your command can be run from Discord at all:

cheatsRequired makes no difference: commands run by a script work with cheats off. If your command changes settings that only operators should touch, GameDirectors is the level to use.

There's no player behind it

Run from Discord, your command comes from the server: origin.sourceType is Server and origin.sourceEntity is undefined. A command that acts on "the player who typed it" has nobody to act on, so check rather than assume:

customCommandRegistry.registerCommand(
  {
    name: "myaddon:option",
    description: "Sets your option.",
    permissionLevel: CommandPermissionLevel.GameDirectors,
    cheatsRequired: false,
    mandatoryParameters: [{ name: "value", type: CustomCommandParamType.Integer }],
  },
  (origin, value) => {
    const player = origin.sourceEntity;
    if (player?.typeId !== "minecraft:player") {
      return { status: CustomCommandStatus.Failure, message: "Run this as a player." };
    }
    system.run(() => player.setDynamicProperty("myaddon:option", value));
    return { status: CustomCommandStatus.Success };
  },
);

Minecraft's execute supplies the player. Run like this, origin.sourceEntity is Steve, exactly as if he'd typed it himself:

/relay run command: execute as Steve run myaddon:option 12

Commands that act on the whole world need neither.

What Discord sees

Discord is told whether the command worked, and nothing more. Minecraft gives a script a command's success, not its output, so the message you return never reaches Discord. Minecraft's own syntax errors do, such as a missing argument.

If someone in Discord needs to know what happened, post it yourself with a discord:message script event. It goes to the channels the owner chose for those messages.

Script events work too

If your addon listens for script events instead of registering commands, those can be run from Discord the same way:

/relay run command: scriptevent myaddon:reward Steve
/relay run command: execute as Steve run scriptevent myaddon:reward

Your system.afterEvents.scriptEventReceive handler gets the first with sourceType Server, and the second with Steve as sourceEntity. Both work on Realms with cheats off.

What to tell owners

Owners allow commands by name, so tell them which names to allow on the Commands tab: myaddon:option, say. To use execute as, they allow execute as well. BedrockRelay checks the command after run against the same list, so allowing execute doesn't allow anything else.