Merge pull request #6590 from segmentio/spencerattick-patch-5

Add info about /debug endpoint

Author: forstisabella

Diff for: src/connections/destinations/catalog/actions-google-analytics-4/index.md

@@ -188,6 +188,15 @@ Google doesn't currently support passing certain reserved fields to the Google A
 
 The Google Analytics 4 [debug mode](https://support.google.com/analytics/answer/7201382?hl=en){:target="_blank"} only works with a client-side implementation through gtag.js, Google Tag Manager, or Firebase. Because Segment's Google Analytics 4 Cloud integration is server-side and uses the Measurement Protocol API, debug mode is not supported.
 
+However, you can use Google's `/debug` endpoint to test your events against Google's Measurement Protocol Validation Server. For more information, see Google's [Validate events](https://developers.google.com/analytics/devguides/collection/protocol/ga4/validating-events?client_type=gtag#:~:text=Protocol%20Validation%20Server-,/debug/mp/collect,-All%20other%20request){:target="_blank”} documentation. 
+
+To validate your events:
+
+1. Run a test through Segment's [Event Tester](/docs/connections/test-connections/) with the event you're concerned about. 
+2. Copy the `Request from Segment` value you see. This is the payload that Segment attempts to send to Google.
+3. Use an API testing tool, like Postman, to send that payload to Google's `/debug` endpoint. 
+4. Google's `/debug` endpoint returns a [validation code](https://developers.google.com/analytics/devguides/collection/protocol/ga4/validating-events?client_type=gtag#validation_code){:target="_blank”} and a description of the error. 
+
 ### Mobile data
 
 To achieve complete reporting, Google recommends use of their Firebase SDKs to send mobile data to Google Analytics 4. To assist in your implementation, Segment has a [Firebase destination](/docs/connections/destinations/catalog/firebase) available for mobile analytics. For more information on linking Google Analytics 4 properties to Firebase, see [Google Analytics 4 Firebase integration](https://support.google.com/analytics/answer/9289234?hl=en){:target="_blank"}.