diff --git a/direct-file/scripts/predictable-tin.py b/direct-file/scripts/predictable-tin.py
index a8cfbfc..1bcc3d8 100755
--- a/direct-file/scripts/predictable-tin.py
+++ b/direct-file/scripts/predictable-tin.py
@@ -1,27 +1,35 @@
-#! /usr/bin/env python3
-
-# Simple script to output the TIN that's expected for a given email address for any environment using csp-simulator
-#
-# Usage: ./predictable-tin.py EMAIL_ADDRESS
-
 import sys
 import hashlib
-import typing
+import re
+import argparse
+from typing import Optional
 
-
-def calculate_tin(email: str):
+def calculate_tin(email: str) -> str:
+    """Calculate a predictable TIN based on the email address."""
     # nosemgrep: bandit.B303-2
     sha1 = hashlib.sha1()
     sha1.update(f'{email}:IAL2'.encode('utf-8'))
     predictable_last_four = int.from_bytes(sha1.digest()[0:2], 'big') % 9999
     return f'123-00-{predictable_last_four:04d}'
 
+def is_valid_email(email: str) -> bool:
+    """Simple email validation."""
+    return re.match(r"^[^@\s]+@[^@\s]+\.[^@\s]+$", email) is not None
 
-def main():
-    if (sys.argv.__len__() > 1):
-        print(calculate_tin(sys.argv[1]))
-    else:
-        print(f'Usage: {sys.argv[0]} EMAIL_ADDRESS')
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Predict the TIN for a given email address.")
+    parser.add_argument('email', metavar='EMAIL_ADDRESS', type=str, nargs='?', help='Email address to predict TIN for')
+    args = parser.parse_args()
+
+    if not args.email:
+        parser.print_usage()
+        sys.exit(1)
+
+    if not is_valid_email(args.email):
+        print(f"Error: '{args.email}' is not a valid email address.", file=sys.stderr)
+        sys.exit(1)
+
+    print(calculate_tin(args.email))
 
 if __name__ == '__main__':
     main()