diff --git a/services_api_key_auth.api.php b/services_api_key_auth.api.php
new file mode 100644
index 0000000..13934d0
--- /dev/null
+++ b/services_api_key_auth.api.php
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * @file
+ * Documents Services API Key Auth's hooks for API reference.
+ */
+
+/**
+ * Alter whether the API key is considered valid or not, before the access
+ * callback returns. This allows you to add your own logic to the callback.
+ *
+ * @param &$valid
+ *   Boolean showing whether the API key is already considered valid.
+ *
+ * @param &$args
+ *   Array of arguments passed to the access callback. Can be useful for context.
+ */
+function hook_services_api_key_valid_alter(&$valid, &$args) {
+  if (arg(0) === 'xyz-rest' && arg(1) === 'allow-everyone') {
+    $valid = TRUE;
+  }
+}
diff --git a/services_api_key_auth.module b/services_api_key_auth.module
index 1f4bf5b..d997c7e 100644
--- a/services_api_key_auth.module
+++ b/services_api_key_auth.module
@@ -26,6 +26,8 @@ function services_api_key_auth_services_authenticate() {
   $api_key = (!empty($_REQUEST['api-key'])) ? $_REQUEST['api-key'] : '';
   // Validate request
   $valid = (services_api_key_auth_compare_key($api_key, $args[0]['api_key'])) ? TRUE : FALSE;
+  // Allow other modules to have their say.
+  drupal_alter('services_api_key_valid', $valid, $args);
   if ($valid) {
     // If a valid request, witch to user to perform drupal response.
     if (!empty($args[0]['user'])) {