The "official" way to give commands is to use the cactus: prefix.
When the ProcessMessages option enabled (default), Agave Tequilana will emulate Cactus2001 by also reading "normal" player messages a player sends to themselves. When PHost is being used, these need to start with a '<' marker, but otherwise do not require a prefix:
<Command:> defhw 13
(or build 13) will a cactus on planet 13. In addition, forwarding a planet to yourself in VPA will also cause a cactus to be built:
<<< VPA Data Transmission >>> OBJECT: Planet 13
The 'vote' command is also recognized this way.
Unlike "official" command messages, these messages will echo back to you.