diff --git a/main.py b/main.py
index 7624b05..d805ecd 100644
--- a/main.py
+++ b/main.py
@@ -5,6 +5,7 @@ app = FastAPI()
 
 @app.get("/new_session")
 async def new_session():
+    """Start a new session"""
     # add session to the database
     # return new session cookie
     return {"session_id": 42}
@@ -12,6 +13,7 @@ async def new_session():
 
 @app.get("/next_picture/{session_id}")
 async def next_picture(session_id: int):
+    """Request new picture to rate."""
     # take not rated picture from the database
     # do not insert anything in the database yet
     # return this picture
@@ -20,5 +22,7 @@ async def next_picture(session_id: int):
 
 @app.get("/rate_picture/{session_id}/{picture_id}/{mark}")
 async def rate_picture(session_id: int, picture_id: int, mark: int):
+    """Submit a rating for the picture"""
+    # check if session is valid
     # add new mark to the session table
     pass