Hello. You did not inform the text to which this question refers, which makes it impossible for examples of it to be exposed that prove the ironic tone used by the author. However, I will try to help you in the best possible way by showing you how to recognize an ironic tone.
An ironic tone, within a text is noticeable when the author uses a language that uses words that promote a dignified different from what is being spoken, in addition, this means promotes a subtle and subjunctive humor, which usually criticizes something. An example of an ironic tone, it can happen when a character is on the street and it starts to rain heavily, the character hated that it would happen, but he says "That's great, that's exactly what I wanted."