Martinez says Alcaraz's arrival at Goodison Park will provide the club's other defenders with real competition.
"You don't get the opportunity to sign someone with Antolin's experience in the Premier League on a free transfer very often," Martinez told the Liverpool Echo.
"He was one of the best centre-halves at the World Cup in South Africa in 2010 with Paraguay so for him to come to Everton is the perfect moment in his career.
"And he is going to bring us something to compete with the centre-halves we have at the club. He brings huge experience and a huge desire to be successful at the football club.
"And that is important that every signing has a burning desire to succeed at Everton."