The five-fold ministry consists of apostles, prophets, evangelists, pastors and teachers. These names describe roles in the Church, the Body of Christ. These roles are fulfilled by the anointing of the Holy Spirit and power. See 1 John 2:20, 27.

The role of the apostle is to be an ambassador. "Apostle" means one sent. By implication it means one sent with a message. In the Church when someone is described as being an apostle it means he or she is sent to us with a particular and specific message about the Kingdom of God which the Body of Christ, the Church, needs to hear. It means he or she is moving strongly in the anointing to present that message.

Although the word "apostles" was distinctively applied to the Twelve, nevertheless from the beginning the word "apostle" was also used in its general meaning. Hence, in Acts 14:14 we find Barnabas being referred to as an apostle.

Smith Wigglesworth was an example in the 20th century of an apostle. He was referred to as an apostle of faith. This was because of his particular message about faith. His message opened up to God's people what faith in God and His promises is able to accomplish on earth. The anointing was strongly upon him to present that message.

The apostle Paul outlines how an apostleship is validated in his first letter to the Corinthians. He writes,

Am I not free? Am I not an apostle? Haven't I seen Jesus our Lord? Aren't you the result of my work for the Lord? Even though others may not think of me as an apostle, I am certainly one to you! You are the proof that I am the Lord's apostle. That is what I say to stand up for myself when people judge me.

1 Corinthians 9:1-3 - NIrV

In looking to discern whether it is appropriate to refer to someone as an apostle you might ask, "Is this minister bringing a particular message to us relating to the Kingdom of God? Is the anointing moving on him to deliver that message? Is his or her ministry of that message positively impacting our lives to the glory of God."

If, to the first question, it is pretty clear to you what that message and, to the next two questions, you can confidently answer "Yes" then it is likely that the title of apostle is justified. Otherwise, perhaps this minister might better be referred to as a teacher or an evangelist, for example.