Those addons can be used by Agile Toolkit.

1. Install Agile Toolkit into "atk4"
2. Install addons into "atk4-addons"
3. Inside your API include addons through addLocation():

	$this->addLocation('atk4-addons',array(
		'php'=>array('mvc',
			'billing/lib',
			'misc/lib',
		),
		'template'=>'misc/templates/',
	))->setParent($this->pathfinder->base_location);

Only include search path for addons you will need.
Addons will not be initialized unless you specifically use
them.