diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 7769ef6..3915059 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -1,68 +1,71 @@
 <?php
 
 /**
- * This file is automatically generated. Use 'arc liberate' to rebuild it
+ * This file is automatically generated. Use 'arc liberate' to rebuild it.
  *
  * @generated
  * @phutil-library-version 2
  */
 phutil_register_library_map(array(
   '__library_version__' => 2,
   'class' => array(
     'Diagram' => 'storage/Diagram.php',
     'DiagramApplication' => 'application/DiagramApplication.php',
     'DiagramCelerityResources' => 'celerity/DiagramCelerityResources.php',
     'DiagramContentTransaction' => 'xaction/DiagramContentTransaction.php',
     'DiagramController' => 'controller/DiagramController.php',
     'DiagramDAO' => 'storage/DiagramDAO.php',
     'DiagramPHIDType' => 'phid/DiagramPHIDType.php',
     'DiagramPatchList' => 'storage/patch/DiagramPatchList.php',
     'DiagramReplyHandler' => 'mail/DiagramReplyHandler.php',
     'DiagramSchemaSpec' => 'storage/DiagramSchemaSpec.php',
     'DiagramSearchConduitAPIMethod' => 'conduit/DiagramSearchConduitAPIMethod.php',
     'DiagramTransaction' => 'storage/DiagramTransaction.php',
     'DiagramTransactionEditor' => 'editor/DiagramTransactionEditor.php',
     'DiagramTransactionType' => 'xaction/DiagramTransactionType.php',
     'DiagramUploadConduitAPIMethod' => 'conduit/DiagramUploadConduitAPIMethod.php',
     'DiagramVersion' => 'storage/DiagramVersion.php',
     'PhabricatorDiagramQuery' => 'query/PhabricatorDiagramQuery.php',
     'PhabricatorDiagramTransactionQuery' => 'query/PhabricatorDiagramTransactionQuery.php',
     'PhabricatorDiagramVersionQuery' => 'query/PhabricatorDiagramVersionQuery.php',
     'PhabricatorRemarkupDiagramRule' => 'remarkup/PhabricatorRemarkupDiagramRule.php',
     'PlainHtmlWebpageResponse' => 'response/PlainHtmlWebpageResponse.php',
   ),
   'function' => array(),
   'xmap' => array(
     'Diagram' => array(
       'DiagramDAO',
       'PhabricatorApplicationTransactionInterface',
       'PhabricatorDestructibleInterface',
       'PhabricatorPolicyInterface',
       'PhabricatorSubscribableInterface',
     ),
     'DiagramApplication' => 'PhabricatorApplication',
     'DiagramCelerityResources' => 'CelerityResourcesOnDisk',
     'DiagramContentTransaction' => 'DiagramTransactionType',
     'DiagramController' => 'PhabricatorController',
     'DiagramDAO' => 'PhabricatorLiskDAO',
     'DiagramPHIDType' => 'PhabricatorPHIDType',
     'DiagramPatchList' => 'PhabricatorSQLPatchList',
     'DiagramReplyHandler' => 'PhabricatorApplicationTransactionReplyHandler',
     'DiagramSchemaSpec' => 'PhabricatorConfigSchemaSpec',
     'DiagramSearchConduitAPIMethod' => 'ConduitAPIMethod',
     'DiagramTransaction' => 'PhabricatorModularTransaction',
     'DiagramTransactionEditor' => 'PhabricatorApplicationTransactionEditor',
     'DiagramTransactionType' => 'PhabricatorModularTransactionType',
     'DiagramUploadConduitAPIMethod' => 'ConduitAPIMethod',
     'DiagramVersion' => array(
       'DiagramDAO',
       'PhabricatorDestructibleInterface',
       'PhabricatorPolicyInterface',
     ),
     'PhabricatorDiagramQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorDiagramTransactionQuery' => 'PhabricatorApplicationTransactionQuery',
     'PhabricatorDiagramVersionQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
-    'PhabricatorRemarkupDiagramRule' => 'PhabricatorObjectRemarkupRule',
+    'PhabricatorRemarkupDiagramRule' => array(
+      'PhabricatorObjectRemarkupRule',
+      'RemarkupSyntaxDocumentationProvider',
+    ),
     'PlainHtmlWebpageResponse' => 'AphrontHTMLResponse',
   ),
 ));
diff --git a/src/remarkup/PhabricatorRemarkupDiagramRule.php b/src/remarkup/PhabricatorRemarkupDiagramRule.php
index c9c362f..b0e7be5 100644
--- a/src/remarkup/PhabricatorRemarkupDiagramRule.php
+++ b/src/remarkup/PhabricatorRemarkupDiagramRule.php
@@ -1,103 +1,128 @@
 <?php
 
 require_celerity_resource('diagram-remarkup-image-js', 'diagram-resources');
 require_celerity_resource('diagram-remarkup-image-css', 'diagram-resources');
 
 final class PhabricatorRemarkupDiagramRule
-  extends PhabricatorObjectRemarkupRule {
+  extends PhabricatorObjectRemarkupRule
+  implements RemarkupSyntaxDocumentationProvider {
 
   protected function getObjectNamePrefix() {
     return 'DIAG';
   }
 
   public function getRuleVersion() {
     return '1.0';
   }
 
   protected function loadObjects(array $ids) {
     $viewer = $this->getEngine()->getConfig('viewer');
 
     $objects = id(new PhabricatorDiagramVersionQuery())
       ->setViewer($viewer)
       ->withDiagramIDs($ids)
       ->execute();
 
     return $objects;
   }
 
   protected function renderObjectEmbed(
     $diagram,
     PhabricatorObjectHandle $handle,
     $options) {
 
     if ($options) {
       $params = explode(',', $options);
       $params = array_map('trim', $params);
     } else {
       $params = array();
     }
 
     // Generate the appropriate HTML using the data from the Diagram and
     // file objects.
     $style = '';
     $class = 'diagram-content';
     $alt = '';
 
     $has_layout = false;
     foreach ($params as $param) {
       if (strpos($param, '=') !== false) {
         list($key, $value) = explode('=', $param, 2);
       } else {
         $key = $param;
         $value = null;
       }
       switch ($key) {
         case 'layout':
           $has_layout = true;
           if ($value === 'left') {
             $class .= ' phabricator-remarkup-embed-layout-left';
           } else if ($value === 'right') {
             $class .= ' phabricator-remarkup-embed-layout-right';
           }
           break;
         case 'float':
           $class .= ' phabricator-remarkup-embed-float-left';
           break;
         case 'size':
           if ($value === 'full') {
             $style .= 'width: 100%;';
           }
           break;
         case 'alt':
           $alt = phutil_escape_html($value);
           break;
       }
     }
 
     if ($has_layout == false) {
       $class .= ' phabricator-remarkup-embed-layout-left';
     }
 
     $output = phutil_tag(
       'div',
       array(
         'class' => 'diagram-container',
       ),
       phutil_tag(
         'img',
         array(
           'style' => $style,
           'class' => $class,
           'src' => 'data:image/png;base64,' . $diagram->getBase64Data(),
           'alt' => $alt,
           'data-sigil' => 'diagram-remarkup-image',
           'data-diagram-version' => $diagram->getPHID(),
           'data-diagram-id' => $diagram->getDiagramID(),
           'title' => 'Double click to edit...'
         )
       )
     );
 
     return $output;
   }
+
+  public function getDocumentation() {
+    return <<<EOT
+= Diagrams
+
+Diagrams is a Phorge extension application for
+[[ https://www.drawio.com | diagrams.net (previously draw.io)]] by JGraph.
+
+You can create and store diagrams in your Phorge instance.
+These diagrams can be referenced by means of the `DIAG` token.
+For example: `{DIAG123}`.
+
+When you double click on a diagram, the editor will open the corresponding
+diagram in a new browser tab.
+
+You can create diagrams with multiple pages, but only the first one will be
+visualized in a referenced diagram.
+
+When you modify an existing diagram, a new version will be created.
+You can select older versions in the editor by means of the dropdown in the
+topright corner.
+If you don't see a dropdown, you diagram has only 1 version.
+EOT;
+  }
 }