diff --git a/nest_backend/api_schemas.py b/nest_backend/api_schemas.py
index 8b39f0e..dd70f7a 100644
--- a/nest_backend/api_schemas.py
+++ b/nest_backend/api_schemas.py
@@ -21,6 +21,7 @@ class InputLoginSchema(Schema):
 class ErrorSchema(Schema):
     result = fields.String(description="Contains a string that informs if the procedure was successful.")
     msg = fields.String(description="Contains a description of the error.")
+    code = fields.String(description="Error code")
 
 
 class SuccesSchema(Schema):
diff --git a/nest_backend/errors.py b/nest_backend/errors.py
new file mode 100644
index 0000000..6fd48f7
--- /dev/null
+++ b/nest_backend/errors.py
@@ -0,0 +1,27 @@
+# User errors
+USER_NOT_FOUND = "errorUserNotFound"  # Could not find user
+USER_WRONG_CREDENTIALS = "errorUserWrongCredentials"  # User has given incorrect pair of credentials
+USER_NOT_AUTHORIZED = "errorUserNotAuthorized"  # User is not authorized to proceed
+USER_NOT_ADMIN = "errorUserNotAdmin"  # User is not an admin
+USER_PREVENT_SEPPUKU = "errorUserPreventSeppuku"  # User cannot delete himself
+USER_DELETION_ERROR = "errorDeletionError"  # Something is preventing the deletion of the user
+# Generic
+GENERIC_NOT_FOUND = "errorNotFound"  # Generic 404
+GENERIC_MISSING_FIELDS = "errorMissingFields"  # Generic 400
+GENERIC_ALREADY_EXISTS = "errorAlreadyExists"  # Generic primary key error
+GENERIC_ENUM_INVALID = "errorEnumInvalid"  # The given integer is not a valid one
+GENERIC_UFO = "errorUnknownError"  # The classic 'the hell is this' error
+GENERIC_NO_JSON = "errorNoJson"  # No JSON was given
+# Repository
+REPOSITORY_NOT_FOUND = "errorRepositoryNotFound"  # Repository not found
+REPOSITORY_NOT_OWNER = "errorRepositoryNotOwner"  # The user is not the repository owner
+REPOSITORY_DEPENDENCY_FAILURE = "errorRepositoryDepencencyFailure"  # Something is preventing the repo to go away
+# Conditions
+CONDITION_NOT_FOUND = "errorConditionNotFound"  # Condition not found.
+# Alerts
+ALERT_NOT_FOUND = "errorAlertNotFound"  # Alert not found
+ALERT_NO_NAME = "errorAlertNoName"  # Missing name entry
+ALERT_NO_LIMIT = "errorAlertNoLimit"  # Missing limit entry
+ALERT_NO_WINDOW = "errorAlertNoWindow"  # Missing window entry
+ALERT_NO_EVALUATION = "errorAlertNoEvaluation"  # Missing evalmode entry
+ALERT_DELETION_FAILURE = "errorAlertDeletionFailure"  # Error while deleting alerts
diff --git a/nest_backend/gestione.py b/nest_backend/gestione.py
index 90c8f00..29462b5 100644
--- a/nest_backend/gestione.py
+++ b/nest_backend/gestione.py
@@ -8,6 +8,7 @@ import functools
 from flask_jwt_extended import get_jwt_identity
 from flask import jsonify
 from re import sub
+from .errors import GENERIC_UFO
 
 __all__ = ["authenticate", "identity", "gen_password", "find_user", "admin_or_403",
            "repository_auth", "json_request_authorizer", "json_error",
@@ -84,13 +85,14 @@ def repository_auth(f):
     return func
 
 
-def json_error(msg):
+def json_error(msg, code=GENERIC_UFO):
     """
     Returns an error in json format
+    :param code: the code of the error according to the spec.
     :param msg: the error message.
     :return: a json formatted string.
     """
-    return jsonify({"result": "failure", 'msg': msg})
+    return jsonify({"result": "failure", 'msg': msg, 'code':code})
 
 
 def json_success(data):
diff --git a/nest_backend/routes/repository/alerts/alert.py b/nest_backend/routes/repository/alerts/alert.py
index 1bd67f5..50a63fd 100644
--- a/nest_backend/routes/repository/alerts/alert.py
+++ b/nest_backend/routes/repository/alerts/alert.py
@@ -4,6 +4,7 @@ from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 from flask_cors import cross_origin
 import datetime
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -113,16 +114,14 @@ def page_alert(aid):
     """
     user = find_user(get_jwt_identity())
     alert = Alert.query.filter_by(id=aid).first()
-    if alert.repository_id not in user.owner_of:
-        return json_error("The user is not authorized."), 403
     if not alert:
-        return json_error("Could not find alert."), 404
+        return json_error("Could not find alert.", ALERT_NOT_FOUND), 404
     if alert.repository not in [a.repository for a in user.authorizations] + user.owner_of:
-        return json_error("You are not authorized to proceed."), 403
+        return json_error("You are not authorized to proceed.", USER_NOT_AUTHORIZED), 403
     if request.method == "GET":
         return json_success(alert.to_json()), 200
     if alert.repository not in user.owner_of:
-        return json_error("You are not authorized to proceed."), 403
+        return json_error("You are not authorized to proceed.", REPOSITORY_NOT_OWNER), 403
     if request.method == "PATCH":
         if 'name' in request.json:
             alert.name = request.json['name']
@@ -137,11 +136,11 @@ def page_alert(aid):
             ext.session.delete(alert)
             ext.session.commit()
         except Exception:
-            return json_error("Something went wrong while deleting alert."), 500
+            return json_error("Something went wrong while deleting alert.", ALERT_DELETION_FAILURE), 500
         return json_success("Deletion completed."), 204
     elif request.method == "PUT":
         if not json_request_authorizer(request.json, alert):
-            return json_error("Missing one or more parameters in repository json."), 400
+            return json_error("Missing one or more parameters in repository json.", GENERIC_MISSING_FIELDS), 400
         alert.limit = request.json['limit']
         alert.name = request.json['name']
         alert.window_size = request.json['window_size']
@@ -149,14 +148,14 @@ def page_alert(aid):
             try:
                 alert.evaluation_mode = ConditionMode(mode)
             except KeyError:
-                return json_error("Unknown `type` specified."), 400
+                return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
             except Exception as e:
-                return json_error("Unknown error:" + str(e)), 400
+                return json_error("Unknown error:" + str(e), GENERIC_UFO), 400
         if request.json['conditions'] is not None:
             # Possibile vulnearabilità! Un utente potrebbe aggiungere conditions non del suo repo!
             for c in request.json['conditions']:
                 if c['id'] not in alert.repository.conditions:
-                    return json_error("Stop! You violated the law!"), 403
+                    return json_error("Stop! You violated the law!", USER_NOT_AUTHORIZED), 403
             # Wow very pythonic so much wow
             # Obtain list of no longer needed connections
             to_be_deleted = [c.cid for c in alert.conditions if
diff --git a/nest_backend/routes/repository/alerts/repository_alerts.py b/nest_backend/routes/repository/alerts/repository_alerts.py
index ec066fe..925cd0b 100644
--- a/nest_backend/routes/repository/alerts/repository_alerts.py
+++ b/nest_backend/routes/repository/alerts/repository_alerts.py
@@ -3,6 +3,7 @@ from nest_backend.database import *
 from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 from flask_cors import cross_origin
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -69,30 +70,30 @@ def page_repository_alerts(rid):
 
     repository = Repository.query.filter_by(id=rid).first()
     if not repository:
-        return json_error("Could not find repository"), 404
+        return json_error("Could not find repository", REPOSITORY_NOT_FOUND), 404
     user = find_user(get_jwt_identity())
     if user.email != repository.owner_id:
-        return json_error("You are not authorized."), 403
+        return json_error("You are not authorized.", REPOSITORY_NOT_OWNER), 403
 
     if request.method == "GET":
         return json_success([alert.to_json() for alert in repository.alerts])
 
     if request.method == "POST":
         if 'name' not in request.json:
-            return json_error("Missing name."), 400
+            return json_error("Missing name.", ALERT_NO_NAME), 400
         if 'limit' not in request.json:
-            return json_error('Missing limit'), 400
+            return json_error('Missing limit', ALERT_NO_LIMIT), 400
         if 'window_size' not in request.json:
-            return json_error('Missing window size'), 400
+            return json_error('Missing window size', ALERT_NO_WINDOW), 400
         if (mode := request.json.get("evaluation_mode")) is not None:
             try:
                 mode = ConditionMode(mode)
             except KeyError:
-                return json_error("Unknown `type` specified."), 400
+                return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
             except Exception as e:
-                return json_error("Unknown error:" + str(e)), 400
+                return json_error("Unknown error:" + str(e), GENERIC_UFO), 400
         else:
-            return json_error("Evaluation mode was not provided."), 400
+            return json_error("Evaluation mode was not provided.", ALERT_NO_EVALUATION), 400
 
         alert = Alert(name=request.json['name'], limit=request.json['limit'], window_size=request.json['window_size'],
                       repository_id=rid, evaluation_mode=mode)
@@ -102,7 +103,7 @@ def page_repository_alerts(rid):
             for condition in request.json['conditions']:
                 c = Condition.query.filter_by(id=condition['id']).first()
                 if not c:
-                    return json_error("Could not locate condition."), 404
+                    return json_error("Could not locate condition.", CONDITION_NOT_FOUND), 404
                 conn = MadeOf(aid=alert.id, cid=c.id)
                 ext.session.add(conn)
                 ext.session.commit()
diff --git a/nest_backend/routes/repository/conditions/condition.py b/nest_backend/routes/repository/conditions/condition.py
index 132b708..c8fe3a3 100644
--- a/nest_backend/routes/repository/conditions/condition.py
+++ b/nest_backend/routes/repository/conditions/condition.py
@@ -3,6 +3,7 @@ from nest_backend.database import *
 from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 from flask_cors import cross_origin
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -106,25 +107,25 @@ def page_condition(cid):
     condition = Condition.query.filter_by(id=cid).first()
     user = find_user(get_jwt_identity())
     if not condition:
-        return json_error("Could not find the condition."), 404
+        return json_error("Could not find the condition.", CONDITION_NOT_FOUND), 404
     if condition.repository not in [a.repository for a in user.authorizations] + user.owner_of and not user.isAdmin:
-        return json_error("You lack the authorization to proceed, pal."), 403
+        return json_error("You lack the authorization to proceed, pal.", USER_NOT_AUTHORIZED), 403
     if request.method == "GET":
         return json_success(condition.to_json()), 200
     if condition.repository not in user.owner_of and not user.isAdmin:
-        return json_error("You lack the authorization to proceed, pal."), 403
+        return json_error("You lack the authorization to proceed, pal.", USER_NOT_AUTHORIZED), 403
     if request.method == "PATCH":
         if request.json is None:
-            return json_error("Missing json content."), 400
+            return json_error("Missing json content.", GENERIC_NO_JSON), 400
 
         if (type_ := request.json.get("type")) is not None:
             try:
                 type_ = ConditionType(type_)
                 condition.type = type_
             except KeyError:
-                return json_error("Unknown `type` specified."), 400
+                return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
             except Exception as e:
-                return json_error("Unknown error:" + str(e)), 400
+                return json_error("Unknown error:" + str(e), GENERIC_UFO), 400
 
         if content := request.json.get("content"):
             condition.content = content
diff --git a/nest_backend/routes/repository/conditions/repository_conditions.py b/nest_backend/routes/repository/conditions/repository_conditions.py
index d6cb8c2..963c23b 100644
--- a/nest_backend/routes/repository/conditions/repository_conditions.py
+++ b/nest_backend/routes/repository/conditions/repository_conditions.py
@@ -5,6 +5,7 @@ from nest_backend.gestione import repository_auth, json_error, json_success, Con
 from nest_backend.database import ext
 from flask_cors import cross_origin
 from nest_backend.gestione import hashtag_validator
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -74,34 +75,34 @@ def page_repository_conditions(rid):
 
     repository = Repository.query.filter_by(id=rid).first()
     if not repository:
-        return json_error("Could not find repository"), 404
+        return json_error("Could not find repository", REPOSITORY_NOT_FOUND), 404
     user = find_user(get_jwt_identity())
 
     if user.email != repository.owner_id:
-        return json_error("You are not authorized."), 403
+        return json_error("You are not authorized.", REPOSITORY_NOT_OWNER), 403
 
     if request.method == "GET":
         try:
             return json_success([u.to_json() for u in repository.conditions])
         except Exception as e:
-            return json_error("Unknown error:" + str(e)), 400
+            return json_error("Unknown error:" + str(e), GENERIC_UFO), 400
 
     if request.method == "POST":
         if request.json is None:
-            return json_error("Missing json content."), 400
+            return json_error("Missing json content.", GENERIC_NO_JSON), 400
 
         if (type_ := request.json.get("type")) is None:
-            return json_error("Missing `type` parameter."), 400
+            return json_error("Missing `type` parameter.", GENERIC_MISSING_FIELDS), 400
 
         try:
             type_ = ConditionType(type_)
         except KeyError:
-            return json_error("Unknown `type` specified."), 400
+            return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
         except Exception as e:
             return json_error("Unknown error: " + str(e)), 400
 
         if not (content := request.json.get("content")):
-            return json_error("Missing `content` parameter."), 400
+            return json_error("Missing `content` parameter.", GENERIC_MISSING_FIELDS), 400
         if type_ == ConditionType.hashtag:
             content = hashtag_validator(content)
         condition = Condition(content=content, type=type_, repository_id=rid)
diff --git a/nest_backend/routes/repository/repositories.py b/nest_backend/routes/repository/repositories.py
index 796484a..57bfcc9 100644
--- a/nest_backend/routes/repository/repositories.py
+++ b/nest_backend/routes/repository/repositories.py
@@ -4,6 +4,7 @@ from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 import datetime
 from flask_cors import cross_origin
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -75,23 +76,27 @@ def page_repositories():
         # Users will be tolerated if they change parameters they're not supposed to touch. We'll ignore them for now.
         if not request.json.get("name") or not request.json.get("conditions") or not str(
                 request.json.get("evaluation_mode")):
-            return json_error("Missing arguments."), 400
+            return json_error("Missing arguments.", GENERIC_MISSING_FIELDS), 400
         name = request.json.get("name")
         try:
             evaluation_mode = ConditionMode(request.json['evaluation_mode'])
-        except:  # KeyError
-            return json_error("Unknown `type` specified."), 400
+        except KeyError:
+            return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
         repository = Repository(name=name, owner_id=user.email, is_active=False, evaluation_mode=evaluation_mode)
         ext.session.add(repository)
         ext.session.commit()
-        ids = [c['id'] for c in request.json['conditions'] if c['id']]
+        conditions = [c for c in repository.conditions if c.id not in [a['id'] for a in request.json['conditions'] if
+                                                                   a['id'] in [b.id for b in repository.conditions]]]
+        for c in conditions:
+            ext.session.delete(c)
+            ext.session.commit()
         # Create brand new conditions
         for c in request.json['conditions']:
             if not c['id']:
                 try:
                     type_ = ConditionType(c['type'])
                 except KeyError:
-                    return json_error("Unknown `type` specified."), 400
+                    return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
                 ext.session.add(Condition(type=type_, content=c['content'], repository_id=repository.id))
                 ext.session.commit()
         repository.is_active = True
diff --git a/nest_backend/routes/repository/repository.py b/nest_backend/routes/repository/repository.py
index 7746b41..56687f1 100644
--- a/nest_backend/routes/repository/repository.py
+++ b/nest_backend/routes/repository/repository.py
@@ -4,7 +4,7 @@ from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 from flask_cors import cross_origin
 import datetime
-
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -156,12 +156,12 @@ def page_repository(rid):
     user = find_user(get_jwt_identity())
     repository = Repository.query.filter_by(id=rid).first()
     if not repository:
-        return json_error("Could not find repository."), 404
+        return json_error("Could not find repository.", REPOSITORY_NOT_FOUND), 404
     if request.method == "GET":
         return json_success(repository.to_json()), 200
     elif request.method == "PATCH":
         if repository.owner_id != user.email:
-            return json_error("You are not the owner of this repository."), 403
+            return json_error("You are not the owner of this repository.", REPOSITORY_NOT_OWNER), 403
         if 'name' in request.json:
             repository.name = request.json['name']
         if 'close' in request.json and not repository.end and repository.is_active:
@@ -173,28 +173,28 @@ def page_repository(rid):
             try:
                 evaluation_mode = ConditionMode(request.json['evaluation_mode'])
             except KeyError:
-                return json_error("Unknown `type` specified."), 400
+                return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
             repository.evaluation_mode = evaluation_mode
         ext.session.commit()
         return json_success(repository.to_json()), 204
     elif request.method == "DELETE":
         if repository.owner_id != user.email and not user.isAdmin:
-            return json_error("You are not the owner of this repository."), 403
+            return json_error("You are not the owner of this repository.", REPOSITORY_NOT_OWNER), 403
         try:
             ext.session.delete(repository)
             ext.session.commit()
         except Exception as e:
             ext.session.rollback()
-            return json_error("Cant delete repository because of dependencies."), 500
+            return json_error("Cant delete repository because of dependencies.", REPOSITORY_DEPENDENCY_FAILURE), 500
         return json_success("Success"), 204
     elif request.method == "PUT":
         if not json_request_authorizer(request.json, repository):
-            return json_error("Missing one or more parameters in repository json."), 400
+            return json_error("Missing one or more parameters in repository json.", GENERIC_MISSING_FIELDS), 400
         # Users will be tolerated if they change parameters they're not supposed to touch. We'll ignore them for now.
         try:
             evaluation_mode = ConditionMode(request.json['evaluation_mode'])
         except KeyError:
-            return json_error("Unknown `type` specified."), 400
+            return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
         repository.evaluation_mode = evaluation_mode
         repository.name = request.json['name']
         repository.is_active = request.json['is_active']
@@ -210,7 +210,7 @@ def page_repository(rid):
                 try:
                     type_ = ConditionType(c['type'])
                 except KeyError:
-                    return json_error("Unknown `type` specified."), 400
+                    return json_error("Unknown `type` specified.", GENERIC_ENUM_INVALID), 400
                 content = c['content']
                 if type_ == ConditionType.hashtag:
                     content = hashtag_validator(content)
diff --git a/nest_backend/routes/repository/tweets/repository_tweets.py b/nest_backend/routes/repository/tweets/repository_tweets.py
index aa60f86..beb4e71 100644
--- a/nest_backend/routes/repository/tweets/repository_tweets.py
+++ b/nest_backend/routes/repository/tweets/repository_tweets.py
@@ -5,6 +5,7 @@ from nest_backend.gestione import repository_auth, json_error, json_success, Con
 from nest_backend.database import ext
 from flask_cors import cross_origin
 from nest_backend.gestione import hashtag_validator
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -44,11 +45,11 @@ def page_repository_tweets(rid):
 
     repository = Repository.query.filter_by(id=rid).first()
     if not repository:
-        return json_error("Could not find repository"), 404
+        return json_error("Could not find repository", REPOSITORY_NOT_FOUND), 404
     user = find_user(get_jwt_identity())
 
-    if user.email != repository.owner_id:
-        return json_error("You are not authorized."), 403
+    if user.email != repository.owner_id and user.email not in [a.email for a in Repository.authorizations]:
+        return json_error("You are not authorized.", USER_NOT_AUTHORIZED), 403
 
     if request.method == "GET":
         return json_success([t.tweet.to_json() for t in repository.tweets])
diff --git a/nest_backend/routes/users/login.py b/nest_backend/routes/users/login.py
index 78e4ee4..0178c44 100644
--- a/nest_backend/routes/users/login.py
+++ b/nest_backend/routes/users/login.py
@@ -4,6 +4,7 @@ from nest_backend.gestione import *
 from flask_jwt_extended import create_access_token
 from flask_cors import cross_origin
 from datetime import timedelta, datetime
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -42,4 +43,4 @@ def page_login():
         access_token = create_access_token(identity=email, expires_delta=delta)
         user = find_user(email)
         return json_success({"access_token": access_token, 'user': user.to_json(), "expiration": expiration}), 201
-    return json_error("Bad username or password."), 401
+    return json_error("Bad username or password.", USER_WRONG_CREDENTIALS), 401
diff --git a/nest_backend/routes/users/user.py b/nest_backend/routes/users/user.py
index 92900fa..9251bb7 100644
--- a/nest_backend/routes/users/user.py
+++ b/nest_backend/routes/users/user.py
@@ -3,6 +3,7 @@ from nest_backend.database import *
 from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 from flask_cors import cross_origin
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -117,26 +118,26 @@ def page_user(email):
     user = find_user(get_jwt_identity())
     target = find_user(email)
     if not target:
-        return json_error("Could not locate the user."), 404
+        return json_error("Could not locate the user.", USER_NOT_FOUND), 404
     if request.method == "GET":
         if not email == user.email and not user.isAdmin:
-            return json_error("Thou art not authorized."), 403
+            return json_error("Thou art not authorized.", USER_NOT_AUTHORIZED), 403
         return json_success(target.to_json())
     elif request.method == "DELETE":
         if not user.isAdmin:
-            return json_error("User is not admin."), 403
+            return json_error("User is not admin.", USER_NOT_ADMIN), 403
         if user == target:
-            return json_error("The user cant delete himself. Its a sin."), 406
+            return json_error("The user cant delete himself. Its a sin.", USER_PREVENT_SEPPUKU), 406
         ext.session.delete(target)
         try:
             ext.session.commit()
         except Exception:
             ext.session.rollback()
-            return json_error("Could not delete the user."), 500
+            return json_error("Could not delete the user.", USER_DELETION_ERROR), 500
         return json_success(""), 204  # "The user has been deleted."
     elif request.method == "PATCH":
         if not email == user.email and not user.isAdmin:
-            return json_error("Thou art not authorized."), 403
+            return json_error("Thou art not authorized.", USER_NOT_AUTHORIZED), 403
         target = find_user(email)
         if request.json.get("username"):
             target.username = request.json.get("username")
diff --git a/nest_backend/routes/users/users.py b/nest_backend/routes/users/users.py
index 3847453..45a1670 100644
--- a/nest_backend/routes/users/users.py
+++ b/nest_backend/routes/users/users.py
@@ -3,6 +3,7 @@ from nest_backend.database import *
 from flask_jwt_extended import jwt_required, get_jwt_identity
 from nest_backend.gestione import *
 from flask_cors import cross_origin
+from nest_backend.errors import *
 
 
 @cross_origin()
@@ -65,16 +66,16 @@ def page_users():
     user = find_user(get_jwt_identity())
     if request.method == "GET":
         if not user.isAdmin:
-            return json_error("User is not admin. Thou art not authorized"), 403
+            return json_error("User is not admin. Thou art not authorized", USER_NOT_ADMIN), 403
         users = User.query.all()
         return json_success([user.to_json() for user in users]), 200
     if request.method == "POST":
         if not user.isAdmin:
-            return json_error("User is not admin. Thou art not authorized."), 403
+            return json_error("User is not admin. Thou art not authorized.", USER_NOT_ADMIN), 403
         if not request.json.get("email") or not request.json.get("password") or not request.json.get("username"):
-            return json_error("Missing required fields."), 400
+            return json_error("Missing required fields.", GENERIC_MISSING_FIELDS), 400
         if User.query.filter_by(email=request.json.get("email")).first():
-            return json_error("User already exists."), 406
+            return json_error("User already exists.", GENERIC_ALREADY_EXISTS), 406
         new_user = User(email=request.json.get("email"), password=gen_password(request.json.get("password")),
                         username=request.json.get("username"))
         ext.session.add(new_user)