diff --git a/README.md b/README.md
index 3c601f3..7b57851 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ The following parts of the documentation are generated by `Claude-3.7-Sonnet`.
 
 ## Data Transport
 
-The questionnaire component receives input via the `window.postMessage` API. The parent window should post a message with the following structure:
+The questionnaire component receives input via the `window.postMessage` API (see [MDN documentation](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage) for details). The parent window should post a message with the following structure:
 
 ```javascript
 window.postMessage({
@@ -73,6 +73,7 @@ Each item in the `items` array represents a question with the following structur
   allowAutoNext: true,   // Auto-advance after selection for radio/scale
   darkMode: false,       // Visual theme
   showItemIndex: true,   // Show item index in the header
+  origin: '*',           // Specify the origin to post messages
   lang: 'en-US'          // Language code
 }
 ```