To develop the above posts, you can't but discuss the use of satire in this excellent essay. You need to make sure you are clear with how Swift uses satire to present his arguments, and then identify quotes that you can use to support what you want to say about this essay. It is important to note the hilarious but also monstrous nature of this work, and likewise you need to consider the tone of the speaker and how he presents himself as reasonable.
I agree with post #2. You should be comfortable discussing satire and the elements that are used to develop and compose satire. From here, you can use these elements to help you explicate "A Modest Proposal" to see how each works in the development of Swift's argument. Then you can evaluate the effectiveness of the composition.
I suggest that you look up "A Modest Proposal" on eNotes.com and take a look at the summary of it before you get started. If I were writing a 1- or 2-page critique, I'd also do an internet search--NOT to steal wording, but to see what others have to say about it.
Next, I'd go back and reread the essay, highlighting items that stand out as particularly satirical, ironic, noteworthy. Once you have your items highlighted, you now have material for a rough outline of your critique. Each of your highlighted items could serve as the topic of a body paragraph.
Good luck with your assignment!
If you are writing a criticism of "A Modest Proposal," then you may want to evaluate Swift's use of satire to criticize the British who were figuratively "eating alive" the Irish. (Swift was a champion of the Irish cause.)
"A Modest Proposal" is an example of a most sophisticated satire, so read some professional criticisms before beginning your essay. Remember to find a working definition of satire that you can employ as the guideline for your paper. Take advantage of the sites below. There are several guidelines on writing an essay, so look under the "how-to" topics, as well.