diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 185ea142..e81939e3 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -66,21 +66,19 @@ constant definitions must be done **outside** the `draw()` method's definition.
 step has been "drawn".
 
 When you have done your calculations and produced an image output, you are required
-to set `this.output` to an object similar to what the input object was, and call
-`callback()`.
+to set `this.output` to an object similar to what the input object was, call
+`callback()`, and set `options.step.output` equal to the output DataURL
 
 ### UI Methods
 
 The module is responsible to emit various events for the UI to capture. There are
 four events in all:
 
-* `UI.onSetup()` must be emitted when the module is added. So it must be emitted
-outside the draw method's definition as shown above.
-* `UI.onDraw()` must be emitted whenever the `draw()` method is called. So it should
-ideally be the first line of the definition of the `draw` method.
-* `UI.onComplete(output_src)` must be emitted whenever the output of a draw call
+* `UI.onSetup(options.step)` must be emitted when the module is added. So it must be emitted outside the draw method's definition as shown above.
+* `UI.onDraw(options.step)` must be emitted whenever the `draw()` method is called. So it should ideally be the first line of the definition of the `draw` method.
+* `UI.onComplete(options.step)` must be emitted whenever the output of a draw call
 is ready. An argument, that is the DataURL of the output image must be passed in.
-* `UI.onRemove()` is emitted automatically and the module should not emit it.
+* `UI.onRemove(options.step)` is emitted automatically and the module should not emit it.
 
 To add a module to Image Sequencer, it must have the following method; you can wrap an existing module to add them: