diff --git a/TODO b/TODO
index 7e11633..b41ccde 100644
--- a/TODO
+++ b/TODO
@@ -1,12 +1,10 @@
 - og / json-sd
 - logger
-- bring sections headers on all pages other than home page further up (reduce top margin / padding)
 - set game current position on game load to ply 0 and whatever the FEN is (starting position probably, but could be custom position)
 - privacy policy - have no access to anything you generate, only keep a count of success/failed pdf generations with timestamp and error message
 - a11y and lighthouse fixes
 - check wcag compliance
 - 429 lichess error handling
-- add throw errors or return errors in server code
 - try/catch where needed in client code
 - generate state and check it against the state returned from lichess https://lichess.org/api#tag/oauth/GET/oauth
 - checkbox and toggle disabled states
diff --git a/src/interfaces.ts b/src/interfaces.ts
index 642eaca..ed64d38 100644
--- a/src/interfaces.ts
+++ b/src/interfaces.ts
@@ -1,3 +1,6 @@
+import type { infer } from "zod";
+import type { TokenResponseSchema } from "#/schemas.ts";
+
 export interface IPosition {
 	ply: number;
 	fen: string;
@@ -29,3 +32,18 @@ export interface IGameState {
 	diagrams: IPosition[];
 	diagramClock: boolean;
 }
+
+export interface ITokenData extends infer<typeof TokenResponseSchema> {}
+
+export interface IUserStudy {
+	id: string;
+	name: string;
+	createdAt: number;
+	updatedAt: number;
+}
+
+export interface IUserStudyChapter {
+	chapterId: string;
+	name: string;
+	pgn: string;
+}
diff --git a/src/schemas.ts b/src/schemas.ts
index 20203a3..8a6ee7b 100644
--- a/src/schemas.ts
+++ b/src/schemas.ts
@@ -8,9 +8,9 @@ export const SessionSchema = z.object({
 
 export const TokenResponseSchema = z.object({
 	access_token: z.string(),
-	expires_in: z.number().optional(),
+	expires_in: z.number(),
 	scope: z.string().optional(),
-	token_type: z.string().optional(),
+	token_type: z.string(),
 });
 
 export const LichessAccountSchema = z.object({