diff --git a/app/models/todo.py b/app/models/todo.py
index 9d45143..b8d2604 100644
--- a/app/models/todo.py
+++ b/app/models/todo.py
@@ -2,10 +2,7 @@ from uuid import uuid4
 
 
 class Todo:
-    def __init__(self,
-                 todo_id: str = None,
-                 title: str = '',
-                 is_done: bool = False):
+    def __init__(self, title: str, todo_id: str = None, is_done: bool = False):
         self.todo_id = todo_id or str(uuid4())
         self.title = title
         self.is_done = is_done
diff --git a/app/repositories/todos.py b/app/repositories/todos.py
index 39c9a7d..fd7acf7 100644
--- a/app/repositories/todos.py
+++ b/app/repositories/todos.py
@@ -3,8 +3,8 @@ from typing import List
 from app.models.todo import Todo
 
 todo_list: List[Todo] = [
-    Todo(title='First'),
-    Todo(todo_id="ec73296f-e108-46a3-bfb3-b4237cb072ba", title='Second')
+    Todo(title="First"),
+    Todo(todo_id="ec73296f-e108-46a3-bfb3-b4237cb072ba", title="Second"),
 ]
 
 
diff --git a/app/schema/mutations/mutation.py b/app/schema/mutations/mutation.py
index d2c4e40..83490f6 100644
--- a/app/schema/mutations/mutation.py
+++ b/app/schema/mutations/mutation.py
@@ -1,12 +1,12 @@
 import graphene
 
-from app.schema.mutations.todo import CreateTodo, DeleteTodo, CloseTodo, UpdateTodo
+from app.schema.mutations.todo import CloseTodo, CreateTodo, DeleteTodo, UpdateTodo
 from app.schema.mutations.user import (
-    CreateUser,
-    UpdateUser,
-    DeleteUser,
     AssignTodoToUser,
+    CreateUser,
     DeassignTodoToUser,
+    DeleteUser,
+    UpdateUser,
 )
 
 
diff --git a/app/schema/mutations/todo/close_todo.py b/app/schema/mutations/todo/close_todo.py
index 2eb4a25..1c71d21 100644
--- a/app/schema/mutations/todo/close_todo.py
+++ b/app/schema/mutations/todo/close_todo.py
@@ -5,6 +5,8 @@ from app.usecases.todo import close_todo
 
 
 class CloseTodo(graphene.Mutation):
+    """Close an existing task"""
+
     class Arguments:
         todo_id = graphene.String(required=True)
 
diff --git a/app/schema/mutations/todo/create_todo.py b/app/schema/mutations/todo/create_todo.py
index a0875c8..9dce25e 100644
--- a/app/schema/mutations/todo/create_todo.py
+++ b/app/schema/mutations/todo/create_todo.py
@@ -5,8 +5,10 @@ from app.usecases.todo import create_todo
 
 
 class CreateTodo(graphene.Mutation):
+    """Create a new task."""
+
     class Arguments:
-        title = graphene.String(default_value="")
+        title = graphene.String(required=True)
 
     result = graphene.Field(TodoResponseField)
 
diff --git a/app/schema/mutations/todo/delete_todo.py b/app/schema/mutations/todo/delete_todo.py
index 6daeeee..106b049 100644
--- a/app/schema/mutations/todo/delete_todo.py
+++ b/app/schema/mutations/todo/delete_todo.py
@@ -5,6 +5,8 @@ from app.usecases.todo import delete_todo
 
 
 class DeleteTodo(graphene.Mutation):
+    """Delete an existing task"""
+
     class Arguments:
         todo_id = graphene.String(required=True)
 
diff --git a/app/schema/mutations/todo/update_todo.py b/app/schema/mutations/todo/update_todo.py
index dc47494..5e1c44b 100644
--- a/app/schema/mutations/todo/update_todo.py
+++ b/app/schema/mutations/todo/update_todo.py
@@ -6,11 +6,13 @@ from app.usecases.todo import update_todo
 
 
 class UpdateTodo(graphene.Mutation):
+    """Update an existing task"""
+
     class Arguments:
         todo = TodoInputType()
 
     result = graphene.Field(TodoResponseField)
 
     def mutate(self, info, todo: Todo):
-        res = update_todo(todo.todo_id, todo.__dict__)
+        res = update_todo(todo.todo_id, vars(todo))
         return UpdateTodo(TodoResponseField(todo=res))
diff --git a/app/schema/mutations/user/__init__.py b/app/schema/mutations/user/__init__.py
index 8156a0b..32f0363 100644
--- a/app/schema/mutations/user/__init__.py
+++ b/app/schema/mutations/user/__init__.py
@@ -1,4 +1,4 @@
+from .assign_todo_to_user import AssignTodoToUser, DeassignTodoToUser
 from .create_user import CreateUser
 from .delete_user import DeleteUser
 from .update_user import UpdateUser
-from .assign_todo_to_user import AssignTodoToUser, DeassignTodoToUser
diff --git a/app/schema/mutations/user/assign_todo_to_user.py b/app/schema/mutations/user/assign_todo_to_user.py
index aed00a0..4844ec8 100644
--- a/app/schema/mutations/user/assign_todo_to_user.py
+++ b/app/schema/mutations/user/assign_todo_to_user.py
@@ -5,6 +5,8 @@ from app.usecases.user import assign_todo_to_user, deassign_todo_to_user
 
 
 class AssignTodoToUser(graphene.Mutation):
+    """Assign an existing task to an existing user"""
+
     class Arguments:
         todo_id = graphene.String()
         user_id = graphene.String()
@@ -21,6 +23,8 @@ class AssignTodoToUser(graphene.Mutation):
 
 
 class DeassignTodoToUser(graphene.Mutation):
+    """Deassign an existing task from an existing user"""
+
     class Arguments:
         todo_id = graphene.String()
         user_id = graphene.String()
diff --git a/app/schema/mutations/user/create_user.py b/app/schema/mutations/user/create_user.py
index 0b27f90..cc08559 100644
--- a/app/schema/mutations/user/create_user.py
+++ b/app/schema/mutations/user/create_user.py
@@ -5,6 +5,8 @@ from app.usecases.user import create_user
 
 
 class CreateUser(graphene.Mutation):
+    """Register an user"""
+
     class Arguments:
         username = graphene.String()
 
diff --git a/app/schema/mutations/user/delete_user.py b/app/schema/mutations/user/delete_user.py
index 19660ce..2ff4940 100644
--- a/app/schema/mutations/user/delete_user.py
+++ b/app/schema/mutations/user/delete_user.py
@@ -5,6 +5,8 @@ from app.usecases.user import delete_user
 
 
 class DeleteUser(graphene.Mutation):
+    """Unregister an existing user"""
+
     class Arguments:
         user_id = graphene.String(required=True)
 
diff --git a/app/schema/mutations/user/update_user.py b/app/schema/mutations/user/update_user.py
index 876713c..10359aa 100644
--- a/app/schema/mutations/user/update_user.py
+++ b/app/schema/mutations/user/update_user.py
@@ -6,6 +6,8 @@ from app.usecases.user import update_user
 
 
 class UpdateUser(graphene.Mutation):
+    """Update user information"""
+
     class Arguments:
         user = UserInputType()
 
diff --git a/app/schema/queries/queries.py b/app/schema/queries/queries.py
index c5c759b..039edd0 100644
--- a/app/schema/queries/queries.py
+++ b/app/schema/queries/queries.py
@@ -1,28 +1,37 @@
 import graphene
 
-from .todo import resolve_get_todo, resolve_list_todos
-from .user import resolve_list_users, resolve_get_user
-from ..types.todo import TodoListResponseField, TodoResponseField
-from ..types.user import UserListResponseField, UserResponseField
+from app.schema.queries.todo import resolve_get_todo, resolve_list_todos
+from app.schema.queries.user import resolve_get_user, resolve_list_users
+from app.schema.types.todo import TodoListResponseField, TodoResponseField
+from app.schema.types.user import UserListResponseField, UserResponseField
 
 
 class Query(graphene.ObjectType):
-    """Schema Queries"""
 
-    """Task Queries"""
-    list_todos = graphene.Field(TodoListResponseField, resolver=resolve_list_todos)
+    # Task Queries
+    list_todos = graphene.Field(
+        TodoListResponseField,
+        resolver=resolve_list_todos,
+        description="List existing tasks",
+    )
 
     get_todo = graphene.Field(
         TodoResponseField,
         todo_id=graphene.String(required=True),
         resolver=resolve_get_todo,
+        description="Retrieve an existing tasks",
     )
 
-    """User Queries"""
-    list_users = graphene.Field(UserListResponseField, resolver=resolve_list_users)
+    # User Queries
+    list_users = graphene.Field(
+        UserListResponseField,
+        resolver=resolve_list_users,
+        description="List registered users",
+    )
 
     get_user = graphene.Field(
         UserResponseField,
         user_id=graphene.String(required=True),
         resolver=resolve_get_user,
+        description="Retrieve a registered user",
     )
diff --git a/app/schema/queries/todo.py b/app/schema/queries/todo.py
index d2d9efa..51ec05c 100644
--- a/app/schema/queries/todo.py
+++ b/app/schema/queries/todo.py
@@ -2,7 +2,7 @@
 Defines the query and how to interact with
 """
 
-from app.schema.types.todo import TodoResponseField, TodoListResponseField
+from app.schema.types.todo import TodoListResponseField, TodoResponseField
 from app.usecases.todo import read_all_todos, read_todo_by_id
 
 
diff --git a/app/schema/types/response.py b/app/schema/types/response.py
index eab61b3..d467afd 100644
--- a/app/schema/types/response.py
+++ b/app/schema/types/response.py
@@ -1,6 +1,8 @@
 import graphene
 
 
-class ResponseField(graphene.ObjectType):
+class ResponseField(graphene.Interface):
+    """Response interface"""
+
     is_success = graphene.Boolean(default_value=True)
     error_message = graphene.String()
diff --git a/app/schema/types/todo.py b/app/schema/types/todo.py
index 46091a9..e3d5cc8 100644
--- a/app/schema/types/todo.py
+++ b/app/schema/types/todo.py
@@ -4,9 +4,7 @@ from app.schema.types.response import ResponseField
 
 
 class TodoType(graphene.ObjectType):
-    """
-    Query Object Type
-    """
+    """Todo Object Type"""
 
     todo_id = graphene.String()
     title = graphene.String(default_value="")
@@ -14,22 +12,26 @@ class TodoType(graphene.ObjectType):
 
 
 class TodoInputType(graphene.InputObjectType):
-    """
-    Mutation Input Object Type
-    """
+    """Todo Input Object"""
 
     todo_id = graphene.String()
     title = graphene.String(default_value="")
     is_done = graphene.Boolean(default_value=False)
 
 
-class TodoResponseField(ResponseField):
+class TodoResponseField(graphene.ObjectType):
+    """Todo response object"""
+
+    class Meta:
+        interfaces = (ResponseField,)
+
     todo = graphene.Field(TodoType)
 
 
-class TodoListResponseField(ResponseField):
+class TodoListResponseField(graphene.ObjectType):
+    """Todos list response object"""
+
+    class Meta:
+        interfaces = (ResponseField,)
+
     todos = graphene.Field(graphene.List(TodoType))
-
-
-class CreateTodoResponseField(ResponseField):
-    todo = graphene.Field(TodoType)
diff --git a/app/schema/types/user.py b/app/schema/types/user.py
index fded72b..75c446a 100644
--- a/app/schema/types/user.py
+++ b/app/schema/types/user.py
@@ -5,19 +5,33 @@ from app.schema.types.todo import TodoType
 
 
 class UserType(graphene.ObjectType):
+    """User schema type"""
+
     user_id = graphene.String()
     username = graphene.String()
     tasks = graphene.List(TodoType)
 
 
 class UserInputType(graphene.InputObjectType):
+    """User input object"""
+
     user_id = graphene.String()
     username = graphene.String()
 
 
-class UserListResponseField(ResponseField):
+class UserListResponseField(graphene.ObjectType):
+    """User list response object"""
+
+    class Meta:
+        interfaces = (ResponseField,)
+
     users = graphene.List(UserType)
 
 
-class UserResponseField(ResponseField):
+class UserResponseField(graphene.ObjectType):
+    """User response object"""
+
+    class Meta:
+        interfaces = (ResponseField,)
+
     user = graphene.Field(UserType)
diff --git a/app/usecases/todo/create_todo.py b/app/usecases/todo/create_todo.py
index 7ee4c71..751ea50 100644
--- a/app/usecases/todo/create_todo.py
+++ b/app/usecases/todo/create_todo.py
@@ -2,5 +2,5 @@ from app.models.todo import Todo
 from app.repositories.todos import add_todo
 
 
-def create_todo(title: str = '') -> Todo:
+def create_todo(title: str) -> Todo:
     return add_todo(title)
diff --git a/app/usecases/todo/delete_todo.py b/app/usecases/todo/delete_todo.py
index 54c8dd7..48ef388 100644
--- a/app/usecases/todo/delete_todo.py
+++ b/app/usecases/todo/delete_todo.py
@@ -1,5 +1,5 @@
 from app.models.todo import Todo
-from app.repositories.todos import todo_exists, remove_todo
+from app.repositories.todos import remove_todo, todo_exists
 
 
 def delete_todo(todo_id: str) -> Todo:
diff --git a/app/usecases/user/assign_todo_to_user.py b/app/usecases/user/assign_todo_to_user.py
index 70229fa..c94d2bd 100644
--- a/app/usecases/user/assign_todo_to_user.py
+++ b/app/usecases/user/assign_todo_to_user.py
@@ -1,4 +1,4 @@
-from app.models import User, Todo
+from app.models import Todo, User
 from app.repositories.users import add_todo_to_user, remove_todo_from_user
 from app.usecases.todo import read_todo_by_id
 from app.usecases.user.read_user_by_id import read_user_by_id
diff --git a/app/usecases/user/delete_user.py b/app/usecases/user/delete_user.py
index df87c79..8b9bde1 100644
--- a/app/usecases/user/delete_user.py
+++ b/app/usecases/user/delete_user.py
@@ -1,7 +1,7 @@
 from typing import Tuple
 
 from app.models.user import User
-from app.repositories.users import user_exists, remove_user
+from app.repositories.users import remove_user, user_exists
 
 
 def delete_user(user_id: str) -> Tuple[User, bool]:
diff --git a/app/usecases/user/update_user.py b/app/usecases/user/update_user.py
index 242ff7c..e67b294 100644
--- a/app/usecases/user/update_user.py
+++ b/app/usecases/user/update_user.py
@@ -1,7 +1,7 @@
 from typing import Tuple
 
 from app.models.user import User
-from app.repositories.users import user_exists, edit_user
+from app.repositories.users import edit_user, user_exists
 
 
 def update_user(user_id: str, data: dict) -> Tuple[User, bool]: