Improve documentation around go/allowed-deps-error

Bug: 264349293
Change-Id: I64e95938e53fb26c104e0daece4939f97744a344
diff --git a/apex/apex_singleton.go b/apex/apex_singleton.go
index 6faed70..1581949 100644
--- a/apex/apex_singleton.go
+++ b/apex/apex_singleton.go
@@ -55,17 +55,17 @@
 			   touch ${out};
 			else
 				echo -e "\n******************************";
-				echo "ERROR: go/apex-allowed-deps-error";
+				echo "ERROR: go/apex-allowed-deps-error contains more information";
 				echo "******************************";
 				echo "Detected changes to allowed dependencies in updatable modules.";
 				echo "To fix and update packages/modules/common/build/allowed_deps.txt, please run:";
 				echo -e "$$ (croot && packages/modules/common/build/update-apex-allowed-deps.sh)\n";
 				echo "When submitting the generated CL, you must include the following information";
 				echo "in the commit message if you are adding a new dependency:";
-				echo "Apex-Size-Increase:";
-				echo "Previous-Platform-Support:";
-				echo "Aosp-First:";
-				echo "Test-Info:";
+				echo "Apex-Size-Increase: Expected binary size increase for affected APEXes (or the size of the .jar / .so file of the new library)";
+				echo "Previous-Platform-Support: Are the maintainers of the new dependency committed to supporting previous platform releases?";
+				echo "Aosp-First: Is the new dependency being developed AOSP-first or internal?";
+				echo "Test-Info: What’s the testing strategy for the new dependency? Does it have its own tests, and are you adding integration tests? How/when are the tests run?";
 				echo "You do not need OWNERS approval to submit the change, but mainline-modularization@";
 				echo "will periodically review additions and may require changes.";
 				echo -e "******************************\n";