diff --git a/app/main.py b/app/main.py
index 27b7a42..9c4afa0 100644
--- a/app/main.py
+++ b/app/main.py
@@ -81,11 +81,11 @@ async def get_current_user(token: str = Depends(oauth2_scheme)) -> User:
     return user_serialize(user)
 
 
-# Routes - TODO: find workaround to display 401/409/... HTTP error codes in openapi.json 
+# Routes
 @app.post(
     path="/register",
     response_model=Token,
-    responses={409: {"model": Message}}
+    responses={409: {"model": HTTPError}}
 )
 async def register(user: UserRegisterDTO):
     user_exists = users_collection.find_one({"username": user.username})
@@ -106,7 +106,7 @@ async def register(user: UserRegisterDTO):
 @app.post(
     path="/login", 
     response_model=Token,
-    responses={401: {"model": Message}}
+    responses={401: {"model": HTTPError}}
 )
 async def login(form_data: OAuth2PasswordRequestForm = Depends()):
     user = users_collection.find_one({"username": form_data.username})
@@ -124,7 +124,7 @@ async def login(form_data: OAuth2PasswordRequestForm = Depends()):
 
 @app.get(
     path="/logout",
-    responses={401: {"model": Message}}
+    responses={401: {"model": HTTPError}}
 )
 async def logout(current_user: User = Depends(get_current_user)):
     # TODO: find usecase / what to do ??
@@ -132,18 +132,18 @@ async def logout(current_user: User = Depends(get_current_user)):
 
 @app.get(
     path="/pin/{id}",
-    responses={401: {"model": Message}, 404: {"model": Message}}
+    responses={401: {"model": HTTPError}, 404: {"model": HTTPError}}
 )
 async def get_pin(id: str, current_user: User = Depends(get_current_user)):
     pin = pins_collection.find_one({"_id": ObjectId(id)})
     if pin is None:
         raise HTTPException(status_code=404, detail="Pin not found")
     
-    return pin
+    return pin_serialize(pin)
 
 @app.patch(
     path="/pin/{id}",
-    responses={401: {"model": Message}, 404: {"model": Message}}
+    responses={401: {"model": HTTPError}, 404: {"model": HTTPError}}
 )
 async def update_pin(id: str, pin: Pin, current_user: User = Depends(get_current_user)):
     result = pins_collection.update_one({"_id": ObjectId(id)}, {"$set": pin.model_dump()})
@@ -154,7 +154,7 @@ async def update_pin(id: str, pin: Pin, current_user: User = Depends(get_current
 
 @app.post(
     path="/pin/add",
-    responses={401: {"model": Message}}    
+    responses={401: {"model": HTTPError}}    
 )
 async def add_pin(pin: Pin, current_user: User = Depends(get_current_user)):
     pin_id = pins_collection.insert_one(pin.model_dump()).inserted_id
@@ -162,7 +162,7 @@ async def add_pin(pin: Pin, current_user: User = Depends(get_current_user)):
 
 @app.get(
     path="/pins",
-    responses={401: {"model": Message}}
+    responses={401: {"model": HTTPError}}
 )
 async def list_pins(current_user: User = Depends(get_current_user)):
     pins = pins_serialize(pins_collection.find().to_list())
@@ -170,7 +170,7 @@ async def list_pins(current_user: User = Depends(get_current_user)):
 
 @app.get(
     path="/friend/{id}",
-    responses={401: {"model": Message}, 404: {"model": Message}}
+    responses={401: {"model": HTTPError}, 404: {"model": HTTPError}}
 )
 async def get_friend(id: str, current_user: User = Depends(get_current_user)):
     friend = friends_collection.find_one({"_id": ObjectId(id)})
@@ -181,7 +181,7 @@ async def get_friend(id: str, current_user: User = Depends(get_current_user)):
 
 @app.post(
     path="/friend/add", 
-    responses={401: {"model": Message}, 409: {"model": Message}}
+    responses={401: {"model": HTTPError}, 409: {"model": HTTPError}}
 )
 async def add_friend(friendAdd: FriendAddDTO, current_user: User = Depends(get_current_user)):
     # TODO: test if exists
@@ -201,7 +201,7 @@ async def add_friend(friendAdd: FriendAddDTO, current_user: User = Depends(get_c
 
 @app.delete(
     path="/friend/{id}/delete",
-    responses={401: {"model": Message}, 404: {"model": Message}}
+    responses={401: {"model": HTTPError}, 404: {"model": HTTPError}}
 )
 async def delete_friend(id: str, current_user: User = Depends(get_current_user)):
     result = friends_collection.delete_one({"_id": ObjectId(id)})
@@ -212,7 +212,7 @@ async def delete_friend(id: str, current_user: User = Depends(get_current_user))
 
 @app.patch(
     path="/friend/{id}/accept",
-    responses={401: {"model": Message}, 404: {"model": Message}}
+    responses={401: {"model": HTTPError}, 404: {"model": HTTPError}}
 )
 async def accept_friend(id: str, current_user: User = Depends(get_current_user)):
     result = friends_collection.update_one({"_id": ObjectId(id)}, {"$set": {"status": "accepted"}})
@@ -223,7 +223,7 @@ async def accept_friend(id: str, current_user: User = Depends(get_current_user))
 
 @app.post(
     path="/friend/{id}/deny",    
-    responses={401: {"model": Message}, 404: {"model": Message}}
+    responses={401: {"model": HTTPError}, 404: {"model": HTTPError}}
 )
 async def deny_friend(id: str, current_user: User = Depends(get_current_user)):
     result = friends_collection.update_one({"_id": ObjectId(id)}, {"$set": {"status": "denied"}})
@@ -235,14 +235,14 @@ async def deny_friend(id: str, current_user: User = Depends(get_current_user)):
 @app.get(
     path="/friends",
     response_model=FriendListDTO,
-    responses={401: {"model": Message}}
+    responses={401: {"model": HTTPError}}
 )
 async def list_friends(current_user: User = Depends(get_current_user)):
-    return FriendListDTO(**friends_serialize(friends_collection.find({"user_id": current_user.uid}).to_list(), friends_collection.find({"friend_user_id": current_user.uid})))
+    return FriendListDTO(**friends_serialize(friends_collection.find({"user_id": current_user.uid}).to_list(), friends_collection.find({"friend_user_id": current_user.uid}).to_list()))
 
 @app.get(
     path="/users",
-    responses={401: {"model": Message}, 422: {"model": Message}},
+    responses={401: {"model": HTTPError}, 422: {"model": HTTPError}},
     response_model=list[UserDTO]
 )
 async def search_users(name: str, current_user: User = Depends(get_current_user)):