diff --git a/affinity_effect_calculator/src/affinity_effect_calculator/cli.py b/affinity_effect_calculator/src/affinity_effect_calculator/cli.py
new file mode 100644
index 0000000..aa3049a
--- /dev/null
+++ b/affinity_effect_calculator/src/affinity_effect_calculator/cli.py
@@ -0,0 +1,76 @@
+import argparse
+import json
+import sys
+from pathlib import Path
+from typing import Any, Dict
+
+from affinity_effect_calculator import core
+
+
+def _load_effects(input_path: Path) -> Dict[str, float]:
+    if not input_path.exists() or not input_path.is_file():
+        raise FileNotFoundError(f"Input file not found: {input_path}")
+    with input_path.open('r', encoding='utf-8') as f:
+        data = json.load(f)
+    if not isinstance(data, dict):
+        raise ValueError("Input JSON must be an object with effect_4x and effect_2x fields.")
+    if "effect_4x" not in data or "effect_2x" not in data:
+        raise ValueError("JSON missing required fields: 'effect_4x' and 'effect_2x'.")
+    try:
+        effect_4x = float(data["effect_4x"])
+        effect_2x = float(data["effect_2x"])
+    except (TypeError, ValueError) as e:
+        raise ValueError("Invalid numeric values for effect_4x or effect_2x.") from e
+    return {"effect_4x": effect_4x, "effect_2x": effect_2x}
+
+
+def _save_result(output_path: Path, result_data: Dict[str, Any]) -> None:
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    with output_path.open('w', encoding='utf-8') as f:
+        json.dump(result_data, f, indent=2)
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Berechnet den Affinitäts-Interaktionseffekt basierend auf 4× und 2× Lastwerten."
+    )
+    parser.add_argument(
+        "--input",
+        required=True,
+        help="Pfad zur JSON-Datei mit Eingabewerten."
+    )
+    parser.add_argument(
+        "--output",
+        required=False,
+        default="output/result.json",
+        help="Pfad zur Ergebnisdatei (Standard: output/result.json)."
+    )
+
+    args = parser.parse_args()
+    input_path = Path(args.input)
+    output_path = Path(args.output)
+
+    try:
+        input_data = _load_effects(input_path)
+        calculated_effect = core.calculate_affinity_effect(
+            effect_4x=input_data["effect_4x"],
+            effect_2x=input_data["effect_2x"]
+        )
+
+        result = {
+            "effect_4x": input_data["effect_4x"],
+            "effect_2x": input_data["effect_2x"],
+            "calculated_effect": calculated_effect,
+        }
+
+        print(f"Calculated interaction effect: {calculated_effect}")
+
+        _save_result(output_path, result)
+
+    except Exception as exc:
+        print(f"Error: {exc}", file=sys.stderr)
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()