Merge pull request #7255 from segmentio/spencerattick-patch-5

Add FAQ on Source Function Infinite Looping Error

src/connections/functions/source-functions.md

@@ -438,3 +438,9 @@ The test function interface has a 4KB console logging limit. Outputs surpassing
 #### Can I send a custom response from my Source Function to an external tool?
 
 No, Source Functions can't send custom responses to the tool that triggered the Function's webhook. Source Functions can only send a success or failure response, not a custom one.
+
+#### Why am I seeing the error "Functions are unable to send data or events back to their originating source" when trying to save my Source Function?
+
+This error occurs because Segment prevents Source Functions from sending data back to their own webhook endpoint (`https://fn.segmentapis.com`). Allowing this could create an infinite loop where the function continuously triggers itself.
+
+To resolve this error, check your Function code and ensure the URL `https://fn.segmentapis.com` is not included. This URL is used to send data to a Source Function and shouldn't appear in your outgoing requests. Once you remove this URL from your code, you’ll be able to save the Function successfully.