Tool refers to Newmaker when Paul asks it “Who am I?” The only other references to Newmaker are the “Newmaker Plane” referenced in the note in Care’s room, as well as the answer red tool gives in Petscop 5 to the question “Where am I?”, earning the answer: “under the Newmaker plane”.
The capitalisation of Newmaker is important, as it means that “Newmaker” is a proper Noun- this could then refer to a name or a place.
Most probably a reference to Candace Newmaker, although it is still not clear whether game is referencing Candace or anyone in her family directly, or rather using it as an analogy/clue.
The secret portion of the game may have been developed specifically for this “Newmaker”. Whether Newmaker is meant to refer to the player character, the player (Paul), or the “intended” player, we still don’t know.