diff --git a/src/client.ts b/src/client.ts
index 6657375..c883a97 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -22,6 +22,9 @@ async function request(url: string, method: string) {
   }
 }
 
+export type TuitioToken = { raw: string; validFrom: Date; validUntil: Date };
+export type TuitioAuthenticationResult = { token: TuitioToken; status: string };
+
 class TuitioClient {
   baseUrl: string;
 
@@ -29,7 +32,7 @@ class TuitioClient {
     this.baseUrl = baseUrl;
   }
 
-  async authenticate(userName: string, password: string) {
+  async authenticate(userName: string, password: string): Promise<TuitioAuthenticationResult> {
     const templates = getUrlTemplates(this.baseUrl);
     const url = templates.authentication.replace("{username}", userName).replace("{password}", password);