The ICommandSender interface is used the base of each Entity and also some other types in CraftTweaker.
Each IEntity and IPlayer implements this!

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.command.ICommandSender;

ZenGetter	Return Type
ZenGetter displayName	Return Type string
ZenGetter position	Return Type IBlockPos
ZenGetter world	Return Type IWorld
ZenGetter server	Return Type IServer

Takes a String Returns void (nothing).

ZenScript
 Copy
sender.sendMessage(String text);

Takes an ITextComponent Returns void (nothing).

ZenScript
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sender.sendRichTextMessage(ITextComponent textComponent);