Acts 16:30-31 (RSV) and brought them out and said, “Men, what must I do to be saved?”  And they said, “Believe in the Lord Jesus, and you will be saved, you and your household.”
But of course, Jesus explains what it means to “believe” in Him:
John 14:12 Truly, truly, I say to you, he who believes in me will also do the works that I do; and greater works than these will he do, because I go to the Father.
Matthew 7:14-27 For the gate is narrow and the way is hard, that leads to life, and those who find it are few.  “Beware of false prophets, who come to you in sheep’s clothing but inwardly are ravenous wolves.  You will know them by their fruits. Are grapes gathered from thorns, or figs from thistles?  So, every sound tree bears good fruit, but the bad tree bears evil fruit.  A sound tree cannot bear evil fruit, nor can a bad tree bear good fruit.  Every tree that does not bear good fruit is cut down and thrown into the fire.  Thus you will know them by their fruits.  “Not every one who says to me, `Lord, Lord,’ shall enter the kingdom of heaven, but he who does the will of my Father who is in heaven.  On that day many will say to me, `Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’  And then will I declare to them, `I never knew you; depart from me, you evildoers.’  “Every one then who hears these words of mine and does them will be like a wise man who built his house upon the rock;  and the rain fell, and the floods came, and the winds blew and beat upon that house, but it did not fall, because it had been founded on the rock.  And every one who hears these words of mine and does not do them will be like a foolish man who built his house upon the sand;  and the rain fell, and the floods came, and the winds blew and beat against that house, and it fell; and great was the fall of it.”
Luke 6:46 Why do you call me `Lord, Lord,’ and not do what I tell you?
Jesus Himself explained what was required (not just mere belief!), when asked how one receives eternal life: “Jesus vs. ‘Faith Alone’ (Rich Young Ruler)”. I also found 50 passages having to do with judgment and entrance into heaven. Not one referred to faith alone or faith only.
Thus, if someone wants to simplistically appeal to Acts 16:30-31 (or John 3:16 et al) as some quick formula for “faith alone” as the supposedly biblical way of salvation, they at least need to understand in the context of biblical thought on salvation what it means to “believe” in Jesus Christ.
We all initially or in casual assumption, approach the Bible from a post-Enlightenment [hyper-]”rationalistic” mindset; whereas it has to be understood in terms of 1st century Semitic / Near Eastern culture, which is very different from Greek either/or rationalism. It’s not irrational, but it is a fuller, both/and understanding.
The Bible student must learn about the latter and also realize that the former is a profound influence in how he reads and comprehends the Bible, which has to be largely unlearned.
Photo credit: The Lord’s Prayer, by James Tissot (1836-1902) [public domain / Wikimedia Commons]