diff --git a/app/core/auth/endpoints_auth.py b/app/core/auth/endpoints_auth.py
index df63af2336..121a2d9fbe 100644
--- a/app/core/auth/endpoints_auth.py
+++ b/app/core/auth/endpoints_auth.py
@@ -3,6 +3,7 @@
 import logging
 import urllib.parse
 from datetime import UTC, datetime, timedelta
+from typing import Any
 
 import calypsso
 import jwt
@@ -1046,6 +1047,7 @@ async def introspect_refresh_token(
 
 @router.get(
     "/auth/userinfo",
+    response_model=dict[str, Any],
     status_code=200,
 )
 async def auth_get_userinfo(
diff --git a/app/core/core_endpoints/endpoints_core.py b/app/core/core_endpoints/endpoints_core.py
index cdc8db19fc..18f69b0d6d 100644
--- a/app/core/core_endpoints/endpoints_core.py
+++ b/app/core/core_endpoints/endpoints_core.py
@@ -42,6 +42,7 @@ async def read_information(
 
 @router.get(
     "/privacy",
+    response_model=str,
     status_code=200,
 )
 async def read_privacy(settings: Settings = Depends(get_settings)):
@@ -57,6 +58,7 @@ async def read_privacy(settings: Settings = Depends(get_settings)):
 
 @router.get(
     "/terms-and-conditions",
+    response_model=str,
     status_code=200,
 )
 async def read_terms_and_conditions(settings: Settings = Depends(get_settings)):
@@ -72,6 +74,7 @@ async def read_terms_and_conditions(settings: Settings = Depends(get_settings)):
 
 @router.get(
     "/mypayment-terms-of-service",
+    response_model=str,
     status_code=200,
 )
 async def read_mypayment_tos(settings: Settings = Depends(get_settings)):
@@ -86,6 +89,7 @@ async def read_mypayment_tos(settings: Settings = Depends(get_settings)):
 
 @router.get(
     "/support",
+    response_model=str,
     status_code=200,
 )
 async def read_support(settings: Settings = Depends(get_settings)):
@@ -101,6 +105,7 @@ async def read_support(settings: Settings = Depends(get_settings)):
 
 @router.get(
     "/security.txt",
+    response_model=str,
     status_code=200,
 )
 async def read_security_txt(settings: Settings = Depends(get_settings)):
@@ -115,6 +120,7 @@ async def read_security_txt(settings: Settings = Depends(get_settings)):
 
 @router.get(
     "/.well-known/security.txt",
+    response_model=str,
     status_code=200,
 )
 async def read_wellknown_security_txt(settings: Settings = Depends(get_settings)):
@@ -130,6 +136,7 @@ async def read_wellknown_security_txt(settings: Settings = Depends(get_settings)
 
 @router.get(
     "/robots.txt",
+    response_model=str,
     status_code=200,
 )
 async def read_robots_txt(settings: Settings = Depends(get_settings)):
@@ -145,6 +152,7 @@ async def read_robots_txt(settings: Settings = Depends(get_settings)):
 
 @router.get(
     "/account-deletion",
+    response_model=str,
     status_code=200,
 )
 async def read_account_deletion(settings: Settings = Depends(get_settings)):
diff --git a/app/core/google_api/endpoints_google_api.py b/app/core/google_api/endpoints_google_api.py
index aaf2e79849..0d3db05bd7 100644
--- a/app/core/google_api/endpoints_google_api.py
+++ b/app/core/google_api/endpoints_google_api.py
@@ -23,7 +23,7 @@
 hyperion_error_logger = logging.getLogger("hyperion.error")
 
 
-@router.get("/google-api/oauth2callback", status_code=200)
+@router.get("/google-api/oauth2callback", response_model=str, status_code=200)
 async def google_api_callback(
     request: Request,
     db: AsyncSession = Depends(get_db),
diff --git a/app/core/memberships/endpoints_memberships.py b/app/core/memberships/endpoints_memberships.py
index c8a6e80ca2..aa10883d42 100644
--- a/app/core/memberships/endpoints_memberships.py
+++ b/app/core/memberships/endpoints_memberships.py
@@ -521,7 +521,7 @@ async def delete_user_membership(
 
 @router.post(
     "/memberships/{membership_id}/group/{group_id}/synchronize",
-    status_code=201,
+    status_code=204,
 )
 async def synchronize_membership_with_group(
     membership_id: uuid.UUID,
diff --git a/app/core/mypayment/endpoints_mypayment.py b/app/core/mypayment/endpoints_mypayment.py
index 988c047ed5..b9b022bc32 100644
--- a/app/core/mypayment/endpoints_mypayment.py
+++ b/app/core/mypayment/endpoints_mypayment.py
@@ -340,7 +340,7 @@ async def delete_structure(
 
 @router.post(
     "/mypayment/structures/{structure_id}/init-manager-transfer",
-    status_code=201,
+    status_code=204,
 )
 async def init_transfer_structure_manager(
     structure_id: UUID,
@@ -2213,6 +2213,7 @@ async def validate_can_scan_qrcode(
 @router.post(
     "/mypayment/stores/{store_id}/scan",
     status_code=201,
+    response_model=schemas_mypayment.TransactionBase,
 )
 async def store_scan_qrcode(
     store_id: UUID,
diff --git a/app/core/notification/endpoints_notification.py b/app/core/notification/endpoints_notification.py
index bc0e1ebc93..cd86cc8d56 100644
--- a/app/core/notification/endpoints_notification.py
+++ b/app/core/notification/endpoints_notification.py
@@ -253,7 +253,7 @@ async def send_notification(
 
 @router.post(
     "/notification/test/send",
-    status_code=201,
+    status_code=204,
 )
 async def send_test_notification(
     user_id: str | None = None,
diff --git a/app/core/permissions/endpoints_permissions.py b/app/core/permissions/endpoints_permissions.py
index ea2708f9b3..913b80902b 100644
--- a/app/core/permissions/endpoints_permissions.py
+++ b/app/core/permissions/endpoints_permissions.py
@@ -98,7 +98,7 @@ async def read_permission(
 
 @router.post(
     "/permissions/",
-    status_code=201,
+    status_code=204,
 )
 async def create_permission(
     permission: schemas_permissions.CoreGroupPermission
@@ -124,7 +124,6 @@ async def create_permission(
         await cruds_permissions.create_group_permission(permission, db)
     else:
         await cruds_permissions.create_account_type_permission(permission, db)
-    return {"message": "Permission created successfully"}
 
 
 @router.delete(
diff --git a/app/core/users/endpoints_users.py b/app/core/users/endpoints_users.py
index 3d86bf132d..31a48e8004 100644
--- a/app/core/users/endpoints_users.py
+++ b/app/core/users/endpoints_users.py
@@ -567,7 +567,7 @@ async def activate_user(
 
 @router.post(
     "/users/s3-init",
-    status_code=201,
+    status_code=204,
 )
 async def init_s3_for_users(
     db: AsyncSession = Depends(get_db),
@@ -805,6 +805,7 @@ async def migrate_mail(
 
 @router.get(
     "/users/migrate-mail-confirm",
+    response_model=str,
     status_code=200,
 )
 async def migrate_mail_confirm(
diff --git a/app/utils/tools.py b/app/utils/tools.py
index b79b572ae6..4b9023ad2b 100644
--- a/app/utils/tools.py
+++ b/app/utils/tools.py
@@ -812,7 +812,7 @@ async def execute_async_or_sync_method(
 def patch_identity_in_text(
     text: str,
     settings: "Settings",
-):
+) -> str:
     """
     Patch the given text with the identity of the school.
     This is used to replace the identity placeholders in the legal texts with the values defined in the settings.
diff --git a/tests/core/test_mypayment.py b/tests/core/test_mypayment.py
index aca103ddbc..e3c7eea6b1 100644
--- a/tests/core/test_mypayment.py
+++ b/tests/core/test_mypayment.py
@@ -966,7 +966,7 @@ async def test_transfer_structure_manager_as_manager(
             "new_manager_user_id": ecl_user2.id,
         },
     )
-    assert response.status_code == 201
+    assert response.status_code == 204
 
     response = client.get(
         "/mypayment/structures/confirm-manager-transfer",
diff --git a/tests/core/test_permissions.py b/tests/core/test_permissions.py
index 91198c1fc8..0809649dc5 100644
--- a/tests/core/test_permissions.py
+++ b/tests/core/test_permissions.py
@@ -82,7 +82,7 @@ def test_create_permission(client: TestClient) -> None:
         },
         headers={"Authorization": f"Bearer {admin_token}"},
     )
-    assert response.status_code == 201
+    assert response.status_code == 204
 
     response = client.get(
         f"/permissions/{BookingPermissions.manage_managers.value}",