Update README

README.md

@@ -3,10 +3,8 @@ Puppet Facts Upload
 
 [![Build Status](https://travis-ci.org/Sharpie/puppet-facts_upload.svg?branch=master)](https://travis-ci.org/Sharpie/puppet-facts_upload)
 
-**NOTE:** This module is currently a rough draft and should not be used.
-
 This project re-implements the `puppet facts upload` command and part of the
-associated `pupept/v3/facts` endpoint that [was removed][PUP-2560]. along with
+associated `pupept/v3/facts` endpoint that [was removed][PUP-2560] along with
 the inventory service in Puppet 4.0. These pieces of functionality were useful
 for keeping facts updated outside of catalog compilation.
 
@@ -20,3 +18,67 @@ Re-adding the command and endpoint enables two key use cases:
   - The ability to submit updated facts at the end of an agent run. This allows
     facts to reflect any changes made during catalog application and keeps fact
     data as fresh as possible for PuppetDB queries.
+
+
+## Requirements
+
+This module has been tested against the following versions of Puppet Server and
+Puppet Enterprise running on the following platforms:
+
+  - **Versions:** Puppet Server 5.1.z, PE 2017.3.z
+  - **Platforms:** RedHat 6, 7; Ubuntu 14.04, 16.04; SLES 11, 12
+
+The `facts_upload` module is fairly sensitive to the Puppet Server and PE
+version numbers as the code hooks into several internal APIs in both Puppet
+Server and the `puppet_enterprise` module. The module likely will not work if
+your Puppet Server version or platform doesn't fall within the list above.
+
+Puppet Agent support should be much less restrictive. Generally if the agent
+can request a catalog from a Puppet Server, it should be able to upload facts
+once the `facts_upload` module has been applied to Puppet Server.
+
+
+## Usage
+
+The `facts_upload` module currently provides one class: `facts_upload::server`.
+This class should be applied to all nodes running the `puppetserver` or
+`pe-puppetserver` services and will configure the Puppet Server to mount a
+`/puppet/v3/facts` endpoint and configures `auth.conf` to allow agents to
+upload facts for just their own certnames.
+
+The module also provides some Ruby code which is pluginsynced to agents:
+
+  - `lib/puppet/indirector/facts/rest.rb`
+  - `lib/puppet/face/facts/upload.rb`
+
+Agents may run `puppet facts upload` once pluginsync has completed.
+
+
+## Limitations
+
+This module only provides a subset of the functionality that was removed in
+[PUP-2560][PUP-2560]:
+
+  - A `/puppet/v3/facts` API endpoint for Puppet Server that responds to PUT
+    requests only.
+
+  - A `Puppet::Node::Facts::Rest` indirector terminus that sends requests from
+    agents to the `/puppet/v3/facts` API endpoint of the `server` the agent is
+    configure to talk with.
+
+  - A `puppet facts upload` face that fetches facts from Facter and then
+    uploads them to the `/puppet/v3/facts` API endpoint of the `server` the
+    agent is configured to talk with.
+
+Notably, the following deprecated features have not been restored:
+
+  - Functionality and REST API routes related to the Inventory Service.
+
+  - Functionality and indirector terminii related to  the `store_configs`
+    subsystem.
+
+
+## Development
+
+See the output of `rake -T` for development workflow tasks. More info will be
+added to this section in a future release.