Index: src/wp-admin/includes/plugin-install.php
===================================================================
--- src/wp-admin/includes/plugin-install.php	(revision 34562)
+++ src/wp-admin/includes/plugin-install.php	(working copy)
@@ -22,11 +22,47 @@
  *
  * @since 2.7.0
  *
- * @param string $action
- * @param array|object $args Optional. Arguments to serialize for the Plugin Info API.
- * @return object plugins_api response object on success, WP_Error on failure.
+ * @param string       $action Action to perform: 'query_plugins', 'plugin_information',
+ *                             'hot_tags' or 'hot_categories'.
+ * @param array|object $args   {
+ *     Optional. Array or object of arguments to serialize for the Plugin Info API.
+ *
+ *     @type string  $slug     The slug of a plugin.
+ *     @type int     $per_page Number of plugins per page. Default 24.
+ *     @type int     $number   Number of tags or categories to be queried.
+ *     @type string  $locale   Locale to provide context-sensitive results. Default get_locale().
+ *     @type bool    $is_ssl   Whether  links should be returned with http or https. Default false.
+ *     @type array   $fields   {
+ *         Array of fields which should or should not be returned.
+ *
+ *         @type bool $short_description Short description. Default true.
+ *         @type bool $description       Full description. Default false.
+ *         @type bool $sections          Readme sections: description, installation, faq,
+ *                                       screenshots, other notes, and changelog. Default false.
+ *         @type bool $tested            Compatible up to value. Default true.
+ *         @type bool $requires          Required WordPress version. Default true.
+ *         @type bool $rating            Rating in percent and total number of ratings. Default true.
+ *         @type bool $ratings           Rating for each star (1-5). Default true.
+ *         @type bool $downloaded        Download count. Default true.
+ *         @type bool $downloadlink      Download link for the package. Default true.
+ *         @type bool $last_updated      Date of the last update. Default true.
+ *         @type bool $added             Date when plugin was added to the wordpress.org repo. Default true.
+ *         @type bool $tags              Assigned tags. Default true.
+ *         @type bool $compatibility     WordPress compatibility list. Default true.
+ *         @type bool $homepage          Link to plugin homepage. Default true.
+ *         @type bool $versions          List of all versions. Default false.
+ *         @type bool $donate_link       Donation link. Default true.
+ *         @type bool $reviews           Plugin reviews. Default false.
+ *         @type bool $banners           Links to banner images. Default false.
+ *         @type bool $icons             Links to icons. Default false.
+ *         @type bool $active_installs   Number of active installs. Default false.
+ *         @type bool $group             Assigned group. Default false.
+ *         @type bool $contributors      List of contributors. Default false.
+ *     }
+ * }
+ * @return object|WP_Error Response object on success, WP_Error on failure.
  */
-function plugins_api($action, $args = null) {
+function plugins_api( $action, $args = array() ) {
 
 	if ( is_array( $args ) ) {
 		$args = (object) $args;