An injury to Alvaro Morata saw Costa come off the bench in the first half of Spain's 2-0 win away at Belgium in an international friendly on Thursday, and shortly after coming on he provided the lay off for David Silva's opening goal.
Costa has scored just one goal in 11 appearances for Spain since switching nationalities from his native Brazil in 2014, but defended his performance against Belgium.
"They criticise me a lot and if I played for Real Madrid or Barca and was a natural Spaniard they'd say I had a good game, possibly my best for the team," Costa told reporters on Thursday.
"I didn't score but I can be useful to the team. I participated a lot in the game and I leave here happy, unlike in other games."
Costa has had disciplinary breaches with Chelsea, including being banned for three games for stamping on Liverpool's Emre Can last year, but has largely kept out of trouble while representing Spain.
"I haven't done great things for Spain, I can't lie, but when I play well they should say so. They criticise me for my character, but I also have quality," added Costa.
Silva scored the second goal against Belgium from the penalty spot to round off a comfortable 2-0 win in coach Julen Lopetegui's first game in charge since succeeding Vicente del Bosque.
Lopetegui recalling Costa after Del Bosque left him out of the squad for Euro 2016 was one of a number of eye-catching decisions the new coach made in his first squad announcement, including dropping former captain Iker Casillas.
Spain begin their qualifying campaign for the 2018 World Cup at home to Liechtenstein on Monday and Costa said he is optimistic about his and the team's fortunes under the former Porto and Spain under-21 coach.
"A new era has started. I have faith in my team mates," Costa said. "It's true that I have unfinished business with scoring but today I felt good and the goals will come.
"I'd be more concerned if I didn't have chances, but the team is creating them and that's good. I will score soon."
(Reporting by Richard Martin; editing by Sudipto Ganguly)
