According to Catholic Tradition, did God create people to be prophets or did He choose people to be prophets based on good works? According to Catholic Tradition, did God create people to be prophets? Or did he choose people to be prophets based on good works?

For example, before Isaiah was born, did God know that he would be a prophet? Or did God choose Isaiah after he performed good works or proved his suitability to be a prophet in some way?
The Catholic Church teaches in the Catechism of the Catholic Church that prophecy is a gift:


  CCC 2004 Among the special graces ought to be mentioned the
  graces of state that accompany the exercise of the responsibilities of
  the Christian life and of the ministries within the Church:
  
  Having gifts that differ according to the grace given to us, let us
  use them: if prophecy, in proportion to our faith; if service, in our
  serving; he who teaches, in his teaching; he who exhorts, in his
  exhortation; he who contributes, in liberality; he who gives aid, with
  zeal; he who does acts of mercy, with cheerfulness.1
  
  1. Rom 12:6-8.


This article Prophecy | New Advent says:


The gift of prophecy is an extraordinary grace bestowed by God. It has never been confined to any particular tribe, family, or class of persons. There is no distinct faculty in human nature by which any normal or abnormal person can prophesy, neither is any special preparation required beforehand for the reception of this gift.
Writing on the recipients of prophecy, Benedict XIV (Heroic Virtue, III, 144, 150) says: "The recipients of prophecy may be angels, devils, men, women, children, heathens, or gentiles; nor is it necessary that a man should be gifted with any particular disposition in order to receive the light of prophecy provided his intellect and senses be adapted for making manifest the things which God reveals to him. Though moral goodness is most profitable to a prophet, yet it is not necessary in order to obtain the gift of prophecy." He also tells us that the angels by their own natural penetration cannot know future events which are undermined and contingent or uncertain, neither can they know the secrets of the heart of another, whether man or angel.


Answer

From the foregoing, it is clear the gift of prophecy is an extraordinary grace bestowed by God upon whomever he chooses however unworthy (who is ever really worthy) they may be.

Did God create people to be prophets? God chooses or using Biblical and Church language, God chooses and calls whomever he chooses to whatever ministry he calls them to and this includes the prophetic ministry2.

Does God choose people to be prophets based on good works? From the foregoing, no he doesn't. Even devils may be the recipients of prophecy.

The initiative is always God's, his choice free and not dependent in any way on the recipient or their merits.

2. cf. Jn 15:15-17, I Cor:1:2, etc.



Endnote

In Num 11:29 Moses wished:


  29 But Moses said to him, “Are you jealous for my sake? Would that all the Lord’s people were prophets, that the Lord would put his
  spirit upon them!”


Thanks to the gift of God the Father through His Son, Jesus, by the working of the Holy Spirit, all the baptized share in the prophetic mission of Christ beyond Moses' expectations.


  CCC 1268 The baptized have become "living stones" to be
  "built into a spiritual house, to be a holy priesthood."3
  By Baptism they share in the priesthood of Christ, in his prophetic
  and royal mission. They are "a chosen race, a royal priesthood, a holy
  nation, God's own people, that [they] may declare the wonderful deeds
  of him who called [them] out of darkness into his marvelous
  light."4 Baptism gives a share in the common priesthood of
  all believers.
  
  3. 1 Pet 2:5.
  4. 1 Pet 2:9.