To answer this question, I will simply survey and quote from the various creeds and confessions.
The Apostles’ Creed
…Maker of Heaven and Earth
God made everything including you.
The Nicene Creed
…of all things visible and invisible
The Nicene Creed expands upon the Apostles’ Creed statement, making it clear that God did indeed make everything.
The Belgic Confession
We all believe in our hearts
and confess with our mouths
that there is a single
whom we call God—
and the overflowing source
of all good.
The Belgic Confession gets even more detailed, describing God as simple (having no parts or dependencies) and spiritual. The next attributes described are self explanatory, but they describe God by what He is not (via negativa). He is not visible, thus He is invisible.
The Westminster Confession of Faith has three paragraphs describing who God is (WCF II:1-3). I will not repeat them here, instead I will repeat the Westminster Larger Catechism.
The Larger Catechism
Q. 7. What is God?
A. God is a Spirit, in and of himself infinite in being,glory, blessedness, and perfection; all-sufficient, eternal,unchangeable, incomprehensible, every where present, almighty, knowing all things, most wise, most holy, most just, most merciful and gracious, long-suffering, and abundant in goodness and truth.
The answer to Question 7 is similar to the Belgic Confession, although it expands upon it, and describes God (mostly) by what He is.
Now notice I framed the title of this letter in contrast to Question 7. Question 7 asks what, I ask who. I don’t know why the Westminster divines used what instead of who. That’s some history I’ll have to look in to. But offhand without any research, I would say they were mistaken to use that phrasing. You wouldn’t go up to someone and ask them, “What is your father?” you would ask them “Who is your father?” because a father is a person. And this leads me to my final point: all of the confessions and creeds imply that God is a person, (three persons in one essence really) but they don’t come outright and say it. Remember, we can use adjectives to describe what God is, and what He is not, but we must remember that He is a living being, the living God, a person(s), not just a thing to study. We must do this with fear and trembling.