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+++ b/doc/source/index.rst
@@ -1,14 +1,60 @@
-.. cloudkitty documentation master file, created by
-   sphinx-quickstart on Wed May 14 23:05:42 2014.
-   You can adapt this file completely to your liking, but it should at least
-   contain the root `toctree` directive.
-
 ======================================
 Welcome to CloudKitty's documentation!
 ======================================
 
-CloudKitty is a Rating As A Service project aimed at translating metrics
-to prices.
+What is CloudKitty ?
+====================
+
+CloudKitty is a **Rating-as-a-Service** project for OpenStack and more.
+The project aims at being a **generic** solution for the chargeback and rating
+of a cloud. Historically, it was only possible to operate it inside of an
+OpenStack context, but it is now possible to run CloudKitty in standalone mode.
+
+CloudKitty allows to do metric-based rating: it polls endpoints in order to
+retrieve measures and metadata about specific metrics, applies rating rules to
+the collected data and pushes the rated data to its storage backend.
+
+CloudKitty is highly modular, which makes it easy to add new features.
+
+.. note::
+
+   **We're looking for contributors!** If you want to contribute, please have
+   a look at the `developer documentation`_ .
+
+.. _developer documentation: developer/index.html
+
+What can be done with CloudKitty ? What can't ?
+===============================================
+
+**With Cloudkitty, it is possible to:**
+
+- Collect metrics from OpenStack (through Gnocchi and Monasca) or from
+  somewhere else (through Gnocchi in standalone mode and Prometheus). Metric
+  collection is **highly customizable**.
+
+- Apply rating rules to the previous metrics through the `hashmap`_ module or
+  `custom scripts`_. This is all done via CloudKitty's API.
+
+- Retrieve the rated information through the API, grouped by scope and/or by
+  metric type.
+
+**However, it is not possible to:**
+
+- Limit resources in other OpenStack services once a certain limit has been
+  reached. Ex: block instance creation in Nova above a certain price.
+  Cloudkitty does **rating and only rating**.
+
+- Add taxes, convert between currencies, etc... This needs to be done by a
+  billing software. CloudKitty associates a price to a metric for a given
+  period, but the price's unit is what you decide it to be: euros, dollars,
+  cents, squirrels...
+
+.. _hashmap: user/rating/hashmap.html
+
+.. _custom scripts: user/rating/pyscripts.html
+
+Documentation contents
+======================
 
 .. list-table::
    :header-rows: 1