diff --git a/acegen/scoring_functions/__init__.py b/acegen/scoring_functions/__init__.py
index 596be1ff..55988b89 100644
--- a/acegen/scoring_functions/__init__.py
+++ b/acegen/scoring_functions/__init__.py
@@ -1,6 +1,55 @@
+from typing import Callable
+
+from numpy import ndarray
+from torch import Tensor
+
 from acegen.scoring_functions.base import Task
 from acegen.scoring_functions.chemistry import QED
 
 custom_scoring_functions = {
     "QED": QED,
 }
+
+
+def check_scoring_function(scoring_function):
+    """Check if the scoring function is a valid scoring function."""
+    # Check it is a callable
+    if not isinstance(scoring_function, Callable):
+        raise ValueError(
+            f"scoring_function must be a callable, got {type(scoring_function)}"
+        )
+
+    # Check it accepts a single smiles and returns typing number of a tensor
+    if not isinstance(scoring_function("CCO"), (int, float, list, Tensor, ndarray)):
+        raise ValueError(
+            f"scoring_function must return a number, got {type(scoring_function('CCO'))}"
+        )
+
+    # Check it accepts a single smiles and returns a list of number or a tensor
+    scores = scoring_function(["CCO", "CCC"])
+    if not isinstance(scores, (list, Tensor, ndarray)):
+        raise ValueError(
+            f"scoring_function must return a list of number, got {type(scoring_function(['CCO', 'CCC']))}"
+        )
+
+    # If scores is a list, check that each element is a number
+    if isinstance(scores, list):
+        for score in scores:
+            if not isinstance(score, (int, float)):
+                raise ValueError(
+                    f"scoring_function must return a list of number, got {type(scoring_function(['CCO', 'CCC']))}"
+                )
+
+
+def register_custom_scoring_function(name, scoring_function):
+    """Register a custom scoring function.
+
+    Example:
+        >>> from acegen import register_custom_scoring_function, custom_scoring_functions
+        >>> from my_module import my_scoring_function
+        >>> register_custom_scoring_function("my_scoring_function", my_scoring_function)
+        >>> custom_scoring_functions["my_scoring_function"]
+    """
+    check_scoring_function(scoring_function)
+    custom_scoring_functions[name] = scoring_function
+