Laravel - Artisan Console - Input Descriptions
You may assign descriptions to input arguments and options by separating the argument name from the description using a colon. If you need a little extra room to define your command, feel free to spread the definition across multiple lines:
/**
* The name and signature of the console command.
*
* @var string
*/
protected $signature = 'mail:send
{user : The ID of the user}
{ --queue= : Whether the job should be queued}';