When using commands, you want certain commands to only run on a server or in private messages etc.
Most other CommandHandlers uses boolean properties like guildOnly.
To avoid having a ton of these, I imagined a system where you have command tags and for every call, tags of the command are verified one by one.
And this system works very smoothly !
So if you're using the default message event (see how to use defaults events), tags will be checked.

example

if (command.tags.includes(Tag.guildOnly) && !message.guild) {
    message.channel.send(`You must be on a guild to execute the ${command.name} command !`);
}