Improve the top-level command descriptions even further

README.md

@@ -13,13 +13,18 @@ This package implements the following commands:
 
 ### wp cache
 
-Manage the object cache.
+Manipulate the WP Object Cache object.
 
 ~~~
 wp cache
 ~~~
 
-Use a persistent object cache drop-in to persist cache values between requests.
+By default, the WP Object Cache exists in PHP memory for the length of the
+request (and is emptied at the end). Use a persistent object cache drop-in
+to persist the object cache between requests.
+
+[Read the codex article](https://codex.wordpress.org/Class_Reference/WP_Object_Cache)
+for more detail.
 
 **EXAMPLES**
 
@@ -35,12 +40,16 @@ Use a persistent object cache drop-in to persist cache values between requests.
 
 ### wp transient
 
-Manage transients.
+Manipulate the WordPress Transient Cache.
 
 ~~~
 wp transient
 ~~~
 
+By default, the transient cache uses the WordPress database to persist values
+between requests. When a persistent object cache drop-in is installed, the
+transient cache also uses the WordPress Object Cache.
+
 **EXAMPLES**
 
     # Set transient.

src/Cache_Command.php

@@ -1,11 +1,14 @@
 <?php
 
 /**
- * Manipulates the WP Object Cache.
+ * Manipulate the WP Object Cache object.
  *
+ * By default, the WP Object Cache exists in PHP memory for the length of the
+ * request (and is emptied at the end). Use a persistent object cache drop-in
+ * to persist the object cache between requests.
  *
- * Use a persistent object cache drop-in to persist cache values between requests.
- * [WP Object Cache](https://codex.wordpress.org/Class_Reference/WP_Object_Cache)
+ * [Read the codex article](https://codex.wordpress.org/Class_Reference/WP_Object_Cache)
+ * for more detail.
  *
  * ## EXAMPLES
  *

src/Transient_Command.php

@@ -1,7 +1,11 @@
 <?php
 
 /**
- * Manage WordPress transient and standardized way of storing cached data in the database temporarily base.
+ * Manipulate the WordPress Transient Cache.
+ *
+ * By default, the transient cache uses the WordPress database to persist values
+ * between requests. When a persistent object cache drop-in is installed, the
+ * transient cache also uses the WordPress Object Cache.
  *
  * ## EXAMPLES
  *