diff --git a/README.md b/README.md
index c711287..573622a 100644
--- a/README.md
+++ b/README.md
@@ -1,11 +1,24 @@
 # Go Omaha
 
-Implementation of the omaha protocol in Go.
+[![Build Status](https://travis-ci.org/coreos/go-omaha.svg?branch=master)](https://travis-ci.org/coreos/go-omaha)
+[![GoDoc](https://godoc.org/github.com/coreos/go-omaha/omaha?status.svg)](https://godoc.org/github.com/coreos/go-omaha/omaha)
 
-https://github.com/google/omaha
+Implementation of the [omaha update protocol](https://github.com/google/omaha) in Go.
 
-## Docs
+## Status
 
-http://godoc.org/github.com/coreos/go-omaha/omaha
+This code is targeted for use with CoreOS's [CoreUpdate](https://coreos.com/products/coreupdate/) product and the Container Linux [update_engine](https://github.com/coreos/update_engine).
+As a result this is not a complete implementation of the [protocol](https://github.com/google/omaha/blob/master/doc/ServerProtocolV3.md) and inherits a number of quirks from update_engine.
+These differences include:
 
-[![Build Status](https://travis-ci.org/coreos/go-omaha.png)](https://travis-ci.org/coreos/go-omaha)
+ - No offline activity tracking.
+   The protocol's ping mechanism allows for tracking application usage, reporting the number of days since the last ping and how many of those days saw active usage.
+   CoreUpdate does not use this, instead assuming update clients are always online and checking in once every ~45-50 minutes.
+   Each check in should include a ping and optionally an update check.
+
+ - Various protocol extensions/abuses.
+   update_engine, likely due to earlier limitations of the protocol and Google's server implementation, uses a number of non-standard fields.
+   For example, packing a lot of extra attributes such as the package's SHA-256 hash into a "postinstall" action.
+   As much as possible the code includes comments about these extensions.
+
+ - Many data fields not used by CoreUpdate are omitted.