City made it a perfect six Premier League wins from six under Guardiola after Aguero scored in each half - including a 65th-minute penalty after Michael van der Hoorn brought down Kevin de Bruyne.
But Guardiola's team were made to work hard for their win, and they could not relax until Raheem Sterling wrapped it up 13 minutes from time.
"Congratulations to him (Aguero), especially for his first goal," Guardiola said. "I am so happy for him, but he knows I want more.
"He can play better, he can make other things that are going to help us.
"In the box, he is going to help us a lot. His first control for the opening goal was outstanding, but I want to help him be a better player."
Asked about Kevin De Bruyne's situation, Guardiola added: "I think he is injured. We go back to Manchester tonight, and he will be seen by a doctor tomorrow.
"The way he reacted, it looked like muscular, but I am not a doctor, fortunately.
"It is not easy to play twice in four days against the same team (City beat Swansea in the EFL Cup on Wednesday). They started really well.
"We didn't create too many chances early in the game, then (Fernando) Llorente scored a fantastic goal. We attacked their central defenders, but we missed the last pass many times.
"Now, we have two games before a break. We go into the Champions League and then we go to White Hart Lane to play one of the best teams (Spurs) in the last two years to see our level there."