diff --git a/tools/run.py b/tools/run.py
index 3dcbb3e..8dbd8d1 100755
--- a/tools/run.py
+++ b/tools/run.py
@@ -16,6 +16,41 @@
 script = sys.argv[1]
 base_path = Path(f"scripts/{script}")
 
+# ---------------------------------------------------
+# Load script metadata
+# ---------------------------------------------------
+model_path = base_path / "model.json"
+meta_path = base_path / "meta.json"
+
+if not model_path.exists():
+    raise RuntimeError(f"Missing model.json in {base_path}")
+
+with open(model_path, "r", encoding="utf-8") as f:
+    model = json.load(f)
+
+meta = {}
+if meta_path.exists():
+    with open(meta_path, "r", encoding="utf-8") as f:
+        meta = json.load(f)
+
+output_format = meta.get("output_format")
+
+
+def first_variable_name(model_key, fallback_name):
+    variables = model.get(model_key) or []
+    if not variables:
+        return fallback_name
+
+    name = variables[0].get("name")
+    if not name:
+        raise RuntimeError(f"First {model_key} entry in model.json is missing a name")
+
+    return name
+
+
+input_name = first_variable_name("inputVariables", "data_in")
+output_name = first_variable_name("outputVariables", "data_out")
+
 # ---------------------------------------------------
 # Load raw input (format-agnostic)
 # ---------------------------------------------------
@@ -28,21 +63,9 @@
     test_input = f.read()
 
 payload = {
-    "data_in": test_input
+    input_name: test_input
 }
 
-# ---------------------------------------------------
-# Load meta data (optional, for format hints)
-# ---------------------------------------------------
-meta_path = base_path / "meta.json"
-
-meta = {}
-if meta_path.exists():
-    with open(meta_path, "r", encoding="utf-8") as f:
-        meta = json.load(f)
-
-output_format = meta.get("output_format")
-
 # ---------------------------------------------------
 # Headers
 # ---------------------------------------------------
@@ -76,10 +99,10 @@
 # ---------------------------------------------------
 # Validate output
 # ---------------------------------------------------
-if "data_out" not in data:
-    raise RuntimeError(f"No data_out in response: {data}")
+if output_name not in data:
+    raise RuntimeError(f"No {output_name} in response: {data}")
 
-output = data["data_out"]
+output = data[output_name]
 
 if output is None or (isinstance(output, str) and not output.strip()):
     raise RuntimeError("Script returned empty output")
@@ -118,4 +141,4 @@
 else:
     print(str(output)[:500])
 
-print(f"\n>>> Saved as tests/output.{output_format if output_format != 'Base64' else 'bin'}")
\ No newline at end of file
+print(f"\n>>> Saved as tests/output.{output_format if output_format != 'Base64' else 'bin'}")