diff --git a/types/passport/index.d.ts b/types/passport/index.d.ts
index 935ee96966..0e612810d4 100644
--- a/types/passport/index.d.ts
+++ b/types/passport/index.d.ts
@@ -77,10 +77,46 @@ declare namespace passport {
     }
 
     interface StrategyCreatedStatic {
+        /**
+         * Authenticate `user`, with optional `info`.
+         *
+         * Strategies should call this function to successfully authenticate a
+         * user.  `user` should be an object supplied by the application after it
+         * has been given an opportunity to verify credentials.  `info` is an
+         * optional argument containing additional user information.  This is
+         * useful for third-party authentication strategies to pass profile
+         * details.
+         */
         success(user: object, info?: object): void;
-        fail(challenge: string, status?: number): void;
+        /**
+         * Fail authentication, with optional `challenge` and `status`, defaulting
+         * to 401.
+         *
+         * Strategies should call this function to fail an authentication attempt.
+         */
+        fail(challenge?: string | number, status?: number): void;
+        /**
+         * Redirect to `url` with optional `status`, defaulting to 302.
+         *
+         * Strategies should call this function to redirect the user (via their
+         * user agent) to a third-party website for authentication.
+         */
         redirect(url: string, status?: number): void;
+        /**
+         * Pass without making a success or fail decision.
+         *
+         * Under most circumstances, Strategies should not need to call this
+         * function.  It exists primarily to allow previous authentication state
+         * to be restored, for example from an HTTP session.
+         */
         pass(): void;
+        /**
+         * Internal error while performing authentication.
+         *
+         * Strategies should call this function when an internal error occurs
+         * during the process of performing authentication; for example, if the
+         * user directory is not available.
+         */
         error(err: any): void;
     }