File description token does not work

Oh, I also switched to using field_info_fields(), to resolve the outstanding todo. Now, file_filefield_paths_get_fields looks a lot more like image_filefield_paths_get_fields.

As of Drupal 7.6, [file:description] has been removed from core. See #978028: File token fixes: [file:description] does not exist and [file:owner] not using format_username.

In case anyone needs a temporary solution (like me), you can add this token in a custom module.

/**
 * Implements hook_token_info().
 * 
 * Exposes the [file:description] token, which is no longer part of core, and
 * which cannot be implemented in Token until the following issues are
 * resolved, and which point this and custom_tokens should both be removed.
 * 
 * @see #1225762
 * @see #691078
 */
function custom_token_info() {
  $info['tokens']['file']['description'] = array(
    'name' => t('File description'),
    'description' => t('An optional human-readable description of the file.'),
  );
  return $info;
}

/**
 * Implements hook_tokens().
 * 
 * @see custom_token_info()
 */
function custom_tokens($type, $tokens, array $data = array(), array $options = array()) {
  $replacements = array();
  $sanitize = !empty($options['sanitize']);
  if ($type == 'file' && !empty($data['file']) && !empty($data['node'])) {
    $fields = field_info_fields();
    foreach ($fields as $name => $field) {
      if ($field['type'] == 'file' && isset($data['node']->{$field['field_name']}) && is_array($data['node']->{$field['field_name']})) {
        foreach ($data['node']->{$field['field_name']} as $language) {
          foreach ($language as $file) {
            if ($file['fid'] == $data['file']->fid) {
              $replacements[$tokens['description']] = $sanitize ? check_plain($file['description']) : $file['description'];
            }
          }
        }
      }
    }
  }
  return $replacements;
}