The Premier League champions became the first team in history to win 34 top-flight games over a calendar year with the victory.
Ruben Dias, Joao Cancelo, Riyad Mahrez and Raheem Sterling all got on the scoresheet for City at St James’ Park.
Despite recording an eighth consecutive win and going six points clear of third-placed Chelsea, Guardiola was left unimpressed with the collective performance.
“It was an exceptional result and not a good performance at all – especially in the first half.
“The way we played in the first half was one of the poorest of the season.
“The quality of the players made the difference but that is not the way we want to play.
“Of course, in this type of game when you’re not so brilliant or consistent – you miss simple things – you take the result. What we missed were the simple things, not the complicated things,” Guardiola said.