diff --git a/orderly/extract/extractor.py b/orderly/extract/extractor.py
index a205e83c..ba8e4179 100644
--- a/orderly/extract/extractor.py
+++ b/orderly/extract/extractor.py
@@ -1028,7 +1028,7 @@ def contains_transition_metal(agents: AGENTS) -> bool:
                     return True
             return False
 
-        def contains_charcoal(procedure_details) -> bool:
+        def contains_charcoal(procedure_details: str) -> bool:
             if "charcoal" in procedure_details.lower():
                 return True
             return False