diff --git a/metatag.admin.inc b/metatag.admin.inc
index 0b4278a..42a43a9 100644
--- a/metatag.admin.inc
+++ b/metatag.admin.inc
@@ -281,6 +281,8 @@ function metatag_config_edit_form($form, &$form_state, $config) {
     else {
       $options['token types'] = array($contexts[0]);
     }
+    // Allow hook_metatag_token_types_alter() to modify the defined tokens.
+    drupal_alter('metatag_token_types', $options);
   }
 
   // Ensure that this configuration is properly compared to its parent 'default'
diff --git a/metatag.api.php b/metatag.api.php
index b2d97dd..9667092 100644
--- a/metatag.api.php
+++ b/metatag.api.php
@@ -217,3 +217,70 @@ function hook_metatag_page_cache_cid_parts_alter(&$cid_parts) {
  */
 function hook_metatag_presave(&$metatags, $entity_type, $entity_id) {
 }
+
+/**
+ * Allows modules to alter the defined list of tokens available
+ * for metatag patterns replacements.
+ *
+ * By default only context (for example: global, node, etc...)
+ * related tokens are made available to metatag patterns replacements.
+ * This hook allows other modules to extend the default declared tokens.
+ *
+ * @param array $options
+ *   (optional) An array of options including the following keys and values:
+ *   - token types: An array of token types to be passed to theme_token_tree().
+ *   - context: An identifier for the configuration instance type, typically
+ *     an entity name or object name, e.g. node, views, taxonomy_term.
+ *
+ * @see metatag_config_edit_form()
+ * @see metatag_field_attach_form()
+ */
+function hook_metatag_token_types_alter(&$options) {
+  // Watchout: $options['token types'] might be empty
+  if (!isset($options['token types'])) {
+    $options['token types'] = array();
+  }
+
+  if ($options['context'] == 'config1'){
+    $options['token types'] += array('token_type1','token_type2');
+  }
+  elseif ($options['context'] == 'config2'){
+    $options['token types'] += array('token_type3','token_type4');
+  }
+}
+
+/**
+ * Allows modules to alter defined token patterns and values before replacement.
+ *
+ * The metatag module defines default token patterns replacements depending on
+ * the different configuration instances (contexts, such as global, node, ...).
+ * This hook provides an opportunity for other modules to alter the patterns or
+ * the values for replacements, before tokens are replaced (token_replace).
+ *
+ * See facetapi and facetapi_bonus modules for an example of implementation.
+ *
+ * @param $pattern
+ *   A string potentially containing replaceable tokens. The pattern could also
+ *   be altered by reference, allowing modules to implement further logic, such
+ *   as tokens lists or masks/filters.
+ * @param $types
+ *   Corresponds to the 'token data' property of the $options object.
+ *   (optional) An array of keyed objects. For simple replacement scenarios
+ *   'node', 'user', and others are common keys, with an accompanying node or
+ *   user object being the value. Some token types, like 'site', do not require
+ *   any explicit information from $data and can be replaced even if it is
+ *   empty.
+ *
+ * @see DrupalTextMetaTag::getValue()
+ */
+function hook_metatag_pattern_alter(&$pattern, &$types) {
+  if (strpos($pattern, 'token_type1') !== FALSE) {
+    $types['token_type1'] = "data to be used in hook_tokens for replacement";
+  }
+  if (strpos($pattern, 'token_type2') !== FALSE) {
+    // Load something or do some operations.
+    $types['token_type2'] = array("Then fill in the array with the right data");
+    // $pattern could also be altered, for example, strip off [token_type3].
+    $pattern = str_replace('[token_type3]', '', $pattern);
+  }
+}