diff --git a/pipfs_hub/fs.py b/pipfs_hub/fs.py
new file mode 100644
index 0000000..66e0dd5
--- /dev/null
+++ b/pipfs_hub/fs.py
@@ -0,0 +1,5 @@
+from typing import List
+
+def list_packages(root_dir: str) -> List[str]:
+    """Return a list of package names in the given root directory."""
+    # ...