diff --git a/pydropsonde/helper/quality.py b/pydropsonde/helper/quality.py
index 98f2d563..766a8ccf 100644
--- a/pydropsonde/helper/quality.py
+++ b/pydropsonde/helper/quality.py
@@ -82,6 +82,24 @@ def profile_extent(
         alt_dim="gpsalt",
         extent_ratio=0.1,
     ):
+        """
+        Calculate the profile extent quality control flag and details for a given variable.
+
+        This function calculates the altitude of the first measurement for a given variable and checks
+        that this is above a given ratio.
+        Adds the qc flag to the object.
+
+        Parameters:
+            self (object): The object containing the necessary attributes and methods.
+            variable (str): The name of the variable being processed.
+            ds (xarray.Dataset): The dataset containing the variable data.
+            alt_dim (str): The dimension name of the altitude coordinate.
+            extent_ratio (float): The ratio of the drop altitude to the maximum altitude
+                within which the profile is considered valid.
+
+        Returns:
+            None
+        """
         variables = self.qc_vars
         for variable in variables:
             drop_alt = ds.attrs["aircraft_msl_altitude_(m)"]