Paul has undoubtedly heard of what God is doing through the gospel in other places, but his priestly offering that he can take pride in is the work he has done: “I have reason to boast of my work for God” (15:17). He says he will only speak of what Christ has accomplished “through me” to win Gentiles to faith in Jesus Messiah.
Paul sums up his ministry with this: “by word and deed, by the power of signs and wonders, by the power of the Spirit of God … I have fully proclaimed the good news of Christ” (15:18b-19).
Here is a good example of Paul’s ministry — among Gentiles — about which he is proud and about which he will tell (Acts 14:8-18):
8 In Lystra there sat a man who was lame. He had been that way from birth and had never walked. 9 He listened to Paul as he was speaking. Paul looked directly at him, saw that he had faith to be healed 10 and called out, “Stand up on your feet!” At that, the man jumped up and began to walk.
11 When the crowd saw what Paul had done, they shouted in the Lycaonian language, “The gods have come down to us in human form!” 12 Barnabas they called Zeus, and Paul they called Hermes because he was the chief speaker. 13 The priest of Zeus, whose temple was just outside the city, brought bulls and wreaths to the city gates because he and the crowd wanted to offer sacrifices to them.
14 But when the apostles Barnabas and Paul heard of this, they tore their clothes and rushed out into the crowd, shouting: 15 “Friends, why are you doing this? We too are only human, like you. We are bringing you good news, telling you to turn from these worthless things to the living God, who made heaven and earth and sea and everything in them. 16 In the past, he let all nations go their own way. 17 Yet he has not left himself without testimony: He has shown kindness by giving you rain from heaven and crops in their seasons; he provides you with plenty of food and fills your hearts with joy.” 18 Even with these words, they had difficulty keeping the crowd from sacrificing to them.