diff --git a/pkgs/clan-cli/clan_cli/webui/routers/flake.py b/pkgs/clan-cli/clan_cli/webui/routers/flake.py
index 09541803f..c5f15a970 100644
--- a/pkgs/clan-cli/clan_cli/webui/routers/flake.py
+++ b/pkgs/clan-cli/clan_cli/webui/routers/flake.py
@@ -1,4 +1,5 @@
 import json
+from json.decoder import JSONDecodeError
 from pathlib import Path
 
 from fastapi import APIRouter, HTTPException
@@ -11,14 +12,29 @@ from .utils import run_cmd
 router = APIRouter()
 
 
-@router.get("/api/flake/attrs")
-async def inspect_flake_attrs(url: str) -> FlakeAttrResponse:
+async def get_attrs(url: str) -> list[str]:
     cmd = nix_flake_show(url)
     stdout = await run_cmd(cmd)
-    data = json.loads(stdout)
-    nixos_configs = data["nixosConfigurations"]
+
+    data: dict[str, dict] = {}
+    try:
+        data = json.loads(stdout)
+    except JSONDecodeError:
+        raise HTTPException(status_code=422, detail="Could not load flake.")
+
+    nixos_configs = data.get("nixosConfigurations", {})
     flake_attrs = list(nixos_configs.keys())
-    return FlakeAttrResponse(flake_attrs=flake_attrs)
+
+    if not flake_attrs:
+        raise HTTPException(
+            status_code=422, detail="No entry or no attribute: nixosConfigurations"
+        )
+    return flake_attrs
+
+
+@router.get("/api/flake/attrs")
+async def inspect_flake_attrs(url: str) -> FlakeAttrResponse:
+    return FlakeAttrResponse(flake_attrs=await get_attrs(url))
 
 
 @router.get("/api/flake")
diff --git a/pkgs/clan-cli/clan_cli/webui/routers/vms.py b/pkgs/clan-cli/clan_cli/webui/routers/vms.py
index 3011c32c5..2cd37b2bd 100644
--- a/pkgs/clan-cli/clan_cli/webui/routers/vms.py
+++ b/pkgs/clan-cli/clan_cli/webui/routers/vms.py
@@ -3,9 +3,12 @@ import logging
 from typing import Annotated, Iterator
 from uuid import UUID
 
-from fastapi import APIRouter, BackgroundTasks, Body
+from fastapi import APIRouter, BackgroundTasks, Body, status
+from fastapi.exceptions import HTTPException
 from fastapi.responses import StreamingResponse
 
+from clan_cli.webui.routers.flake import get_attrs
+
 from ...nix import nix_build, nix_eval
 from ..schemas import VmConfig, VmCreateResponse, VmInspectResponse, VmStatusResponse
 from ..task_manager import BaseTask, get_task, register_task
@@ -107,5 +110,11 @@ async def get_vm_logs(uuid: UUID) -> StreamingResponse:
 async def create_vm(
     vm: Annotated[VmConfig, Body()], background_tasks: BackgroundTasks
 ) -> VmCreateResponse:
+    flake_attrs = await get_attrs(vm.flake_url)
+    if vm.flake_attr not in flake_attrs:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Provided attribute '{vm.flake_attr}' does not exist.",
+        )
     uuid = register_task(BuildVmTask, vm)
     return VmCreateResponse(uuid=str(uuid))
diff --git a/pkgs/clan-cli/tests/test_flake_api.py b/pkgs/clan-cli/tests/test_flake_api.py
index 767af4f7b..2fa65d281 100644
--- a/pkgs/clan-cli/tests/test_flake_api.py
+++ b/pkgs/clan-cli/tests/test_flake_api.py
@@ -5,7 +5,7 @@ from api import TestClient
 
 
 @pytest.mark.impure
-def test_inspect(api: TestClient, test_flake_with_core: Path) -> None:
+def test_inspect_ok(api: TestClient, test_flake_with_core: Path) -> None:
     params = {"url": str(test_flake_with_core)}
     response = api.get(
         "/api/flake/attrs",
@@ -15,3 +15,16 @@ def test_inspect(api: TestClient, test_flake_with_core: Path) -> None:
     data = response.json()
     print("Data: ", data)
     assert data.get("flake_attrs") == ["vm1"]
+
+
+@pytest.mark.impure
+def test_inspect_err(api: TestClient) -> None:
+    params = {"url": "flake-parts"}
+    response = api.get(
+        "/api/flake/attrs",
+        params=params,
+    )
+    assert response.status_code != 200, "Succeed to inspect vm but expected to fail"
+    data = response.json()
+    print("Data: ", data)
+    assert data.get("detail")