diff --git a/minimax_mcp/utils.py b/minimax_mcp/utils.py
index 0cfdfdf..acee8dc 100644
--- a/minimax_mcp/utils.py
+++ b/minimax_mcp/utils.py
@@ -12,8 +12,17 @@
 def is_file_writeable(path: Path) -> bool:
     if path.exists():
         return os.access(path, os.W_OK)
-    parent_dir = path.parent
-    return os.access(parent_dir, os.W_OK)
+    # The path does not exist yet. Callers create it with
+    # ``mkdir(parents=True)``, which may create several missing levels, so
+    # check the nearest existing ancestor (the directory ``mkdir`` will
+    # actually create entries in) rather than only the immediate parent (which
+    # is itself missing for a multi-level new path). Creating a child in a
+    # directory needs both write and search (execute) permission, so check
+    # ``W_OK | X_OK``.
+    for ancestor in path.parents:
+        if ancestor.exists():
+            return os.access(ancestor, os.W_OK | os.X_OK)
+    return False
 
 
 def build_output_file(
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 13691a1..30503b7 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -16,6 +16,20 @@ def test_is_file_writeable():
         temp_path = Path(temp_dir)
         assert is_file_writeable(temp_path) is True
         assert is_file_writeable(temp_path / "nonexistent.txt") is True
+        # Multi-level new path: the immediate parent does not exist yet, but
+        # mkdir(parents=True) can create it, so it must be reported writeable
+        # (regression: only the immediate parent used to be checked).
+        assert is_file_writeable(temp_path / "a" / "b" / "c") is True
+
+
+def test_build_output_path_creates_nested_dir():
+    # A nested, not-yet-existing output directory must be created rather than
+    # rejected as "not writeable".
+    with tempfile.TemporaryDirectory() as temp_dir:
+        result = build_output_path("a/b/c", temp_dir)
+        assert result == Path(temp_dir) / "a" / "b" / "c"
+        assert result.exists()
+        assert result.is_dir()
 
 
 def test_make_output_file():