diff --git a/features/esm_COPE.py b/features/esm_COPE.py
index f356625..26cc19e 100644
--- a/features/esm_COPE.py
+++ b/features/esm_COPE.py
@@ -128,6 +128,25 @@ DICT_COPE_QUESTION_IDS = {
 
 
 def reassign_question_ids(df_cope_cleaned: pd.DataFrame) -> pd.DataFrame:
+    """
+    Fix question IDs to match their actual content.
+
+    Unfortunately, when altering the protocol to adapt to COVID pandemic,
+    we did not retain original question IDs.
+    This means that for participants before 2021, they are different
+    from for the rest of them.
+    This function searches for question IDs by matching their strings.
+
+    Parameters
+    ----------
+    df_cope_cleaned: pd.DataFrame
+        A cleaned up dataframe, which must also include esm_user_answer_numeric.
+
+    Returns
+    -------
+    df_cope_fixed: pd.DataFrame
+        The same dataframe but with fixed question IDs.
+    """
     df_esm_cope_unique_questions = (
         df_cope_cleaned.groupby("question_id")
         .esm_instructions.value_counts()
diff --git a/features/esm_SAM.py b/features/esm_SAM.py
index a1f46d7..585b9f5 100644
--- a/features/esm_SAM.py
+++ b/features/esm_SAM.py
@@ -447,6 +447,25 @@ def extract_event_duration(df_esm_sam_clean: pd.DataFrame) -> pd.DataFrame:
 
 
 def reassign_question_ids(df_sam_cleaned: pd.DataFrame) -> pd.DataFrame:
+    """
+    Fix question IDs to match their actual content.
+
+    Unfortunately, when altering the protocol to adapt to COVID pandemic,
+    we did not retain original question IDs.
+    This means that for participants before 2021, they are different
+    from for the rest of them.
+    This function searches for question IDs by matching their strings.
+
+    Parameters
+    ----------
+    df_sam_cleaned: pd.DataFrame
+        A cleaned up dataframe, which must also include esm_user_answer_numeric.
+
+    Returns
+    -------
+    df_sam_fixed: pd.DataFrame
+        The same dataframe but with fixed question IDs.
+    """
     df_esm_sam_unique_questions = (
         df_sam_cleaned.groupby("question_id")
         .esm_instructions.value_counts()