Anon-

Here are some verses from the Bible that speak to your question

Gal 1:6-9  I am shocked that you have so quickly turned from God, who chose you because of his wonderful kindness. You have believed another message,  when there is really only one true message. But some people are causing you trouble and want to make you turn away from the good news about Christ.
I pray that God will punish anyone who preaches anything different from our message to you! It doesn't matter if that person is one of us or an angel from heaven.  I have said it before, and I will say it again. I hope God will punish anyone who preaches anything different from what you have already believed.

Paul, who wrote most of the NT says that the message of Jesus should not be altered, or subtracted from, or added to.

Mat 5:17  "Do not think that I came to abolish the Law (Torah) or the Prophets{6. Joshua [יהושע / Y'hoshua]7. Judges [שופטים / Shophtim]8. Samuel (I & II) [שמואל / Sh'muel]9. Kings (I & II) [מלכים / M'lakhim]10. Isaiah [ישעיה / Y'shayahu]11. Jeremiah [ירמיה / Yir'mi'yahu]12. Ezekiel [יחזקאל / Y'khezqel]13. The Twelve Prophets [תרי עשר] a. Hosea [הושע / Hoshea]b. Joel [יואל / Yo'el]c. Amos [עמוס / Amos]d. Obadiah [עובדיה / Ovadyah]e. Jonah [יונה / Yonah]f. Micah [מיכה / Mikhah]g. Nahum [נחום / Nakhum]h. Habakkuk [חבקוק /Havakuk]i. Zephaniah [צפניה / Ts'phanyah]j. Haggai [חגי / Khagai]k. Zechariah [זכריה / Z'kharyah]l. Malachi [מלאכי / Mal'akhi]}

; I did not come to abolish but to fulfill.

Jesus Himself acknowledges the OT's truth and it is implied that there is nothing to be added to it.

Rev 22:18  Here is my warning for everyone who hears the prophecies in this book: If you add anything to them, God will make you suffer all the terrible troubles written in this book.

John the Apostle makes a claim for one of the books that he authored.

GOD works thru people.

The major councils (involved in the canonization) were:

1. 
   1. The Council of Laodicea (A.D. 363) - this particular council accepted all of the books of the New Testament except the Book of Revelation.
2. 
   The Council of Carthage (A.D. 397) - this council of chaired by the preeminent early church father and theologian, Augustine. The Council of Carthage accepted all 27 New Testament books.
3. 
   The Council of Hippo (419 A.D.) - this council reaffirmed the Council of Carthage..

That is about the best that I can do in answering your question.

JayR