diff --git a/unknown_case_counter/src/unknown_case_counter/cli.py b/unknown_case_counter/src/unknown_case_counter/cli.py
new file mode 100644
index 0000000..9d117b9
--- /dev/null
+++ b/unknown_case_counter/src/unknown_case_counter/cli.py
@@ -0,0 +1,37 @@
+import argparse
+import json
+import sys
+from pathlib import Path
+from unknown_case_counter.core import count_unknown_reasons
+
+def _parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(
+        description="Zählt Unknown-Fälle in Delta-Cases nach Ursache.",
+    )
+    parser.add_argument(
+        "--input",
+        required=True,
+        help="Pfad zur CSV-Datei mit Delta-Cases.",
+    )
+    return parser.parse_args()
+
+def main() -> None:
+    args = _parse_args()
+    input_path = Path(args.input)
+
+    # CI-Ready: Validate input file type and existence
+    assert input_path.exists(), f"Input file not found: {input_path}"
+    assert input_path.is_file(), f"Input path is not a file: {input_path}"
+
+    # Call the core function
+    try:
+        summary = count_unknown_reasons(str(input_path))
+    except Exception as exc:
+        print(json.dumps({"error": str(exc)}), file=sys.stderr)
+        sys.exit(1)
+
+    # Output as JSON to stdout
+    json.dump(summary, sys.stdout, indent=2, ensure_ascii=False)
+
+if __name__ == "__main__":
+    main()