Update README.md.

Author: gk-brown

README.md

@@ -14,7 +14,7 @@ Sierra is distributed via Maven Central at [org.httprpc:sierra](https://central.
 
 A [DTD](sierra.dtd) is provided to assist with editing. It is not used for validation and is not required. 
 
-A custom DTD can be generated using the [DTD encoder](sierra-tools/dtd-encoder) tool. An interactive [preview tool](sierra-tools/previewer) is also available.
+A custom DTD can be generated using the [DTD encoder](sierra-tools/dtd-encoder) tool. An interactive [previewer](sierra-tools/previewer) tool is also available. Both can be downloaded [here](https://github.com/HTTP-RPC/Sierra/releases).
 
 # Sierra Classes
 Sierra provides the `UILoader` class, which can be used in conjunction with the following types to to declaratively establish a hierarchy of user interface elements:

sierra-tools/dtd-encoder/README.md

@@ -1,2 +1,24 @@
 # Sierra DTD Encoder
-TODO
+Generates a Sierra DTD file.
+
+## Usage
+```
+dtd-encoder [bindings [classpath]]
+```
+
+The first argument represents the path to a properties file containing the custom bindings. Keys represent markup tags, and values are the fully qualified class names to which the tags will be bound. For example:
+
+```properties
+chart-panel = org.jfree.chart.ChartPanel
+```
+
+The second argument is the path to a directory containing the dependencies (typically the JAR files containing the types to be bound).
+
+Both arguments are relative to the current directory.
+
+If no arguments are provided, the standard Sierra DTD will be generated.
+
+## Example
+```
+$ dtd-encoder bindings.properties build/libs
+```

sierra-tools/previewer/README.md

@@ -1,2 +1,16 @@
-# Sierra Previewer
-TODO
+# Sierra UI Previewer
+Provides a live, interactive preview of Sierra markup.
+
+## Usage
+```
+previewer
+```
+
+Outlets and resource keys are ignored.
+
+## Example
+```
+$ previewer
+```
+
+<img src="README/previewer.png" width="904px"/>