diff --git a/app/main.py b/app/main.py
index bf69788..36c0ffd 100644
--- a/app/main.py
+++ b/app/main.py
@@ -25,7 +25,7 @@ def health_check():
 
 
 @app.get("/sum")
-def compute_sum(a: int = Query(...), b: int = Query(...)):
+def compute_sum(a: int = Query(...), b: int = Query(...)) -> dict[str, int]:
     return {"result": a * b}
 
 
diff --git a/app/store.py b/app/store.py
index 3cb1667..5ea91e3 100644
--- a/app/store.py
+++ b/app/store.py
@@ -1 +1,2 @@
+"""In-memory data store for the Workshop API."""
 profile_store: dict = {}