This cheat will make AI countries say yes/respond favourably to every offer that is made. It is a toggle command - typing it again will turn it off. Note that this will make the AI say yes to offers from other AI countries as well (not just your own).
The syntax for the yesmen command is as follows:
Find below working examples of the yesmen command.
If yesmen is disabled (default), running the above command will enable yesmen. With yesmen enabled, AI nations will respond favourably to ANY offers it receives, including those from other AI nations. Running yesmen again (i.e. whilst yesmen is enabled), will toggle it off.