This can also be achieved by using the console command with the same syntax.Once that is complete you can add a description using the commands provided (see below)

One example of a command is "say RockOn!, $player.name!" which will make the player say RockOn! :p​

Instead of the player saying the line the server will do it.
No big deal, i just noticed and wanted to let you know.
I guess this happens since the new chat features.

runescape

I don't think you can make a player broadcast to chat with native commands.

Players broadcast to chat natively just by talking into chat. Like you said:

runescape

chat.say 0 is to broadcast to Global (0) chat.
chat.say 1 is to broadcast to Team (1) chat.

Good tips, Rune.

@Toliman said "Instead of the player saying the line the server will do it." I presumed he wants the player to "say the line" (lol).