diff --git a/src/Composer/Command/InstallCommand.php b/src/Composer/Command/InstallCommand.php
index 7039cfd10..63804dfad 100644
--- a/src/Composer/Command/InstallCommand.php
+++ b/src/Composer/Command/InstallCommand.php
@@ -28,7 +28,7 @@ class InstallCommand extends Command
     {
         $this
             ->setName('install')
-            ->setDescription('Parses the composer.json file and downloads the needed dependencies.')
+            ->setDescription('Installs the project dependencies from the composer.lock file if present, or falls back on the composer.json.')
             ->setDefinition(array(
                 new InputOption('prefer-source', null, InputOption::VALUE_NONE, 'Forces installation from package sources when possible, including VCS information.'),
                 new InputOption('dry-run', null, InputOption::VALUE_NONE, 'Outputs the operations but will not execute anything (implicitly enables --verbose).'),
@@ -38,9 +38,10 @@ class InstallCommand extends Command
                 new InputOption('verbose', 'v', InputOption::VALUE_NONE, 'Shows more details including new commits pulled in when updating packages.'),
             ))
             ->setHelp(<<<EOT
-The <info>install</info> command reads the composer.json file from the
-current directory, processes it, and downloads and installs all the
-libraries and dependencies outlined in that file.
+The <info>install</info> command reads the composer.lock file from
+the current directory, processes it, and downloads and installs all the
+libraries and dependencies outlined in that file. If the file does not
+exist it will look for composer.json and do the same.
 
 <info>php composer.phar install</info>
 
diff --git a/src/Composer/Command/UpdateCommand.php b/src/Composer/Command/UpdateCommand.php
index 9a5d4a7aa..acf541a3c 100644
--- a/src/Composer/Command/UpdateCommand.php
+++ b/src/Composer/Command/UpdateCommand.php
@@ -27,7 +27,7 @@ class UpdateCommand extends Command
     {
         $this
             ->setName('update')
-            ->setDescription('Updates your dependencies to the latest version, and updates the composer.lock file.')
+            ->setDescription('Updates your dependencies to the latest version according to composer.json, and updates the composer.lock file.')
             ->setDefinition(array(
                 new InputArgument('packages', InputArgument::IS_ARRAY | InputArgument::OPTIONAL, 'Packages that should be updated, if not provided all packages are.'),
                 new InputOption('prefer-source', null, InputOption::VALUE_NONE, 'Forces installation from package sources when possible, including VCS information.'),