Are you trying to control the head movements of a robot, or the bot's avatar?
For robotics you will want to our Bot Libre's command support. A JSON command can be returned as part of a message. The command can be used by the client or app to perform some action, such as moving the head. This is how Bot Libre's virtual assistant support works, commands are used to open apps and send email.
A command can be set in a response, or from a Self script.
For an avatar, you can use actions and poses. If your bot's avatar has a action or pose media file, then you can activate it by setting the action or pose of the response.