Inventorship is a matter of law. Anyone who intellectually contributed to the conception of an inventive idea must be included as an inventor.
Anyone who merely carried out the inventor's instructions during the reduction to practice stage, or acted only as a pair of hands, does not qualify as an inventor.
Accurately identifying all the inventor(s) is a prerequisite for a valid US patent. If you are uncertain who to include as an inventor, you may review how inventorship is determined under US patent law. ITA does not make any inventorship determinations. In case of doubt, the patent attorney who prepares the application is the one who will assist with determining inventorship.