diff --git a/types/index.d.ts b/types/index.d.ts
index d9ad5b3..eaf5c93 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -1,18 +1,21 @@
 import {
   ContextConfigDefault,
-  RouteGenericInterface,
   FastifyInstance,
   FastifyPluginCallback,
   FastifyReply,
   FastifyRequest,
   FastifySchema,
+  RouteGenericInterface,
   preHandlerHookHandler
 } from 'fastify';
 
 declare module 'fastify' {
   interface FastifyInstance<RawServer, RawRequest, RawReply, Logger, TypeProvider> {
-    auth(
-      functions: fastifyAuth.FastifyAuthFunction[] | (fastifyAuth.FastifyAuthFunction | fastifyAuth.FastifyAuthFunction[])[],
+    auth<
+      Request extends FastifyRequest = FastifyRequest,
+      Reply extends FastifyReply = FastifyReply
+    >(
+      functions: fastifyAuth.FastifyAuthFunction<Request, Reply>[] | (fastifyAuth.FastifyAuthFunction<Request, Reply> | fastifyAuth.FastifyAuthFunction<Request, Reply>[])[],
       options?: {
         relation?: fastifyAuth.FastifyAuthRelation;
         run?: 'all';
@@ -26,10 +29,13 @@ type FastifyAuth = FastifyPluginCallback<fastifyAuth.FastifyAuthPluginOptions>
 declare namespace fastifyAuth {
   export type FastifyAuthRelation = 'and' | 'or'
 
-  export type FastifyAuthFunction = (
+  export type FastifyAuthFunction<
+    Request extends FastifyRequest = FastifyRequest,
+    Reply extends FastifyReply = FastifyReply
+  > = (
     this: FastifyInstance,
-    request: FastifyRequest,
-    reply: FastifyReply,
+    request: Request,
+    reply: Reply,
     done: (error?: Error) => void
   ) => void;
 
diff --git a/types/index.test-d.ts b/types/index.test-d.ts
index 6772575..3ab1adb 100644
--- a/types/index.test-d.ts
+++ b/types/index.test-d.ts
@@ -1,4 +1,4 @@
-import fastify, { FastifyRequest, FastifyReply, preHandlerHookHandler, FastifyInstance } from 'fastify';
+import fastify, { FastifyInstance, FastifyReply, FastifyRequest, preHandlerHookHandler } from 'fastify';
 import fastifyAuth from '..'
 import { expectType } from 'tsd';
 import { TypeBoxTypeProvider } from '@fastify/type-provider-typebox'
@@ -57,4 +57,61 @@ jsonSchemaToTS.route({
   url: '/',
   preHandler: jsonSchemaToTS.auth([]),
   handler: () => {}
-})
\ No newline at end of file
+})
+
+declare module "fastify" {
+  interface FastifyRequest {
+    identity: {actorId: string};
+  }
+
+  interface FastifyInstance {
+    authenticate: (request: FastifyRequest) => Promise<void>;
+  }
+}
+
+export const usersMutationAccessPolicy =
+  (fastify: FastifyInstance) =>
+    async (
+      request: FastifyRequest<{
+        Params: { userId: string }
+      }>,
+    ): Promise<void> => {
+      const { actorId } = request.identity;
+      const isOwner = actorId === request.params.userId;
+
+      if (isOwner) {
+        return;
+      }
+
+      fastify.log.warn("Actor should not be able to see this route");
+
+      throw new Error(request.params.userId);
+    };
+
+async function usersController(fastify: FastifyInstance): Promise<void> {
+  fastify.patch<{
+    Params: { userId: string };
+    Body: { name: string };
+  }>(
+    "/:userId",
+    {
+      onRequest: fastify.auth([
+        usersMutationAccessPolicy(fastify),
+      ]),
+    },
+    async (req, res) => ({ success: true }),
+  );
+}
+
+async function usersControllerV2(fastify: FastifyInstance): Promise<void> {
+  fastify.patch<{
+    Params: { userId: string };
+    Body: { name: string };
+  }>(
+    "/:userId",
+    {
+      onRequest: usersMutationAccessPolicy(fastify),
+    },
+    async (req, res) => ({ success: true }),
+  );
+}
\ No newline at end of file