--- a/toolkit/components/telemetry/docs/data/core-ping.rst
+++ b/toolkit/components/telemetry/docs/data/core-ping.rst
@@ -137,28 +137,47 @@ all of the following events occur:
 #. The package install date could not be persisted to disk
 
 The reason we don't just return the package install time even if the date could
 not be persisted to disk is to ensure the value doesn't change once we start
 sending it: we only want to send consistent values.
 
 searches
 ~~~~~~~~
-In the case a search engine is added by a user, the engine identifier "other" is used, e.g. "other.<source>".
+This describes the search engine usage(count). The format is { "<engine identifier>.<source>"" : count }
+This is optional because the users may have never used the search feature.
+There's no difference if extended telemetry is enabled (prerelease builds) or not.
+
+Possible value :
+
+.. code-block:: js
 
-Sources in Android are based on the existing UI telemetry values and are as
-follows:
+    {
+       "yahoo.listitem":2,
+       "duckduckgo.listitem":1,
+       "google-nocodes.suggestion":1
+    }
 
+<engine identifier>:
+The identifier of the the search engine. The identifier is collected the way same as desktop.
+we only record the search engine name when :
+* builtin or suggested search engines with an ID (includes partner search engines in various distribution scenarios).
+  If it's not a built-in engine, we show "null" or "other".
+* If the user has "Health Report" and core ping enabled.
+
+<sources>
+It's from one of the 'method's in UI telemetry. Possible values:
 * actionbar: the user types in the url bar and hits enter to use the default
   search engine
 * listitem: the user selects a search engine from the list of secondary search
   engines at the bottom of the screen
 * suggestion: the user clicks on a search suggestion or, in the case that
   suggestions are disabled, the row corresponding with the main engine
 
+
 Other parameters
 ----------------
 
 HTTP "Date" header
 ~~~~~~~~~~~~~~~~~~
 This header is used to track the submission date of the core ping in the format
 specified by
 `rfc 2616 sec 14.18 <https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.18>`_,