Description says what is there; analysis says what it is doing. Build a thesis one slot at a time — X does Y by means of Z, which matters because W — choosing from options that include the exact wrong turns real drafts make. Watch the sentence assemble on the right, and watch the contestability test flip from fact to claim.
The object you are analyzing
YThe effect — what does it do to someone?
ZThe mechanism — the feature a skeptic could go look at
WThe significance — why a convinced reader should care
Your thesis, assembling
Is there a mechanism? Z has to be checkable.
The disagreement test. Could someone who disagreed with you have written this sentence?
Does it stay in genre? Analysis explains; the moment you rule on good or bad you have become an evaluation.
Paragraph proportions
A thesis is only half the job. Drag the slider to set how your paragraph divides between quoting or describing the evidence and interpreting it. Beginning analysts invert the ratio and wonder why the paragraph reads as summary.
The one-line diagnostic. Could someone who disagreed with you write your topic sentence? If yes, it is a fact, and the paragraph beneath it will be summary no matter how well you write it.