new file mode 100644
--- /dev/null
+++ b/toolkit/components/telemetry/docs/core-ping.rst
@@ -0,0 +1,47 @@
+
+"core" ping
+============
+
+This mobile-specific ping is intended to provide the most critical
+data in a concise format, allowing for frequent uploads.
+
+Since this ping is used to measure retention, it should be sent
+each time the browser is opened.
+
+Submission will be per the Edge server specification::
+
+    /submit/telemetry/docId/docType/appName/appVersion/appUpdateChannel/appBuildID
+
+* ``docId`` is a UUID for deduping
+* ``docType`` is “core”
+* ``appName`` is “Fennec”
+* ``appVersion`` is the version of the application (e.g. "46.0a1")
+* ``appUpdateChannel`` is “release”, “beta”, etc.
+* ``appBuildID`` is the build number
+
+Note: Counts below (e.g. search & usage times) are “since the last
+ping”, not total for the whole application lifetime.
+
+Structure::
+
+    {
+      "v": 1, // ping format version
+      "clientId": <string>, // client id, e.g.
+                            // "c641eacf-c30c-4171-b403-f077724e848a"
+      "seq": <positive integer>, // running ping counter, e.g. 3
+      "locale": <string>, // application locale, e.g. "en-US"
+      "os": <string>, // OS name.
+      "osversion": <string>, // OS version.
+      "device": <string>, // Build.MANUFACTURER + " - " + Build.MODEL
+                          // where manufacturer is truncated to 12 characters
+                          // & model is truncated to 19 characters
+      "arch": <string>, // e.g. "arm", "x86"
+    }
+
+The ``device`` field is filled in with information specified by the hardware
+manufacturer. As such, it could be excessively long and use excessive amounts
+of limited user data. To avoid this, we limit the length of the field. We're
+more likely have collisions for models within a manufacturer (e.g. "Galaxy S5"
+vs. "Galaxy Note") than we are for shortened manufacturer names so we provide
+more characters for the model than the manufacturer.
+

--- a/toolkit/components/telemetry/docs/index.rst
+++ b/toolkit/components/telemetry/docs/index.rst
@@ -14,13 +14,14 @@ Client-side, this consists of:
 
 .. toctree::
    :maxdepth: 2
 
    pings
    common-ping
    environment
    main-ping
+   core-ping
    deletion-ping
    crash-ping
    uitour-ping
    preferences
    crashes