diff --git a/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.cpp b/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.cpp
index c5ca46e6..4c73003e 100644
--- a/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.cpp
+++ b/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.cpp
@@ -33,11 +33,10 @@ StatusCode CellPositionsHCalPhiThetaSegTool::initialize()
   if (m_segmentation == nullptr)
   {
     error() << "There is no phi-theta segmentation!!!!" << endmsg;
-    // return StatusCode::FAILURE;
+    return StatusCode::FAILURE;
   }
   // Take readout bitfield decoder from GeoSvc
   m_decoder = m_geoSvc->getDetector()->readout(m_readoutName).idSpec().decoder();
-  m_volman = m_geoSvc->getDetector()->volumeManager();
 
   // check if decoder contains "layer"
   std::vector<std::string> fields;
@@ -49,9 +48,10 @@ StatusCode CellPositionsHCalPhiThetaSegTool::initialize()
   if (iter == fields.end())
   {
     error() << "Readout does not contain field: 'layer'" << endmsg;
+    return StatusCode::FAILURE;
   }
 
-  // needed to retrieve radii from the dd4hep extension
+  // retrieve radii from the LayeredCalorimeterData extension
   dd4hep::Detector* detector = m_geoSvc->getDetector();
   if (!detector)
   {
@@ -73,8 +73,7 @@ StatusCode CellPositionsHCalPhiThetaSegTool::initialize()
     return StatusCode::FAILURE;
   }
 
-  // Debug information to verify the layers retrieved
-  // m_layersRetrieved is a pointer, then it needs to point to the address of the vector
+  // Debug information to check the number of layers retrieved from the LayeredCalorimeterData extension
   m_layersRetrieved = &(theExtension->layers);
   debug() << "Number of layers retrieved: " << m_layersRetrieved->size() << endmsg;
 
@@ -93,6 +92,14 @@ StatusCode CellPositionsHCalPhiThetaSegTool::initialize()
 
   if (m_detectorName=="HCalThreePartsEndcap")
   {
+    // Check that the vector containing number of layers in each cylinder is provided
+    if (m_numLayersHCalThreeParts.empty())
+    {
+       error() << "The vector m_numLayersHCalThreeParts is empty." << endmsg;
+       return StatusCode::FAILURE;
+    }
+    // Check that the total number of layers provided in the steering file
+    // matches the total number of layers in the geometry xml file
     for (unsigned int i=0; i<m_numLayersHCalThreeParts.size(); i++) 
     {
       numLayersProvided += m_numLayersHCalThreeParts[i];
@@ -164,12 +171,16 @@ int CellPositionsHCalPhiThetaSegTool::layerId(const uint64_t &aCellId)
   return layer;
 }
 
+// calculate layer radii from LayeredCalorimeterData extension
+// which is included in the geometry description
 std::vector<double> CellPositionsHCalPhiThetaSegTool::calculateLayerRadii(unsigned int startIndex, unsigned int endIndex) {
   std::vector<double> radii;
 
   for (unsigned int idxLayer = startIndex; idxLayer < endIndex; ++idxLayer) {
     const dd4hep::rec::LayeredCalorimeterStruct::Layer & theLayer = m_layersRetrieved->at(idxLayer);
+    // inner radius of a given layer
     double layerInnerRadius = theLayer.distance;
+    // radial dimension of a given layer
     double layerThickness = theLayer.sensitive_thickness;
 
     // Calculate mid-radius for the current layer (layerInnerRadius+layerOuterRadius)/2
@@ -180,16 +191,18 @@ std::vector<double> CellPositionsHCalPhiThetaSegTool::calculateLayerRadii(unsign
   return radii;
 }
 
-// to be used for HCalTileBarrel 
+// calculateLayerRadii should be used for HCalTileBarrel which is formed
+// by a single cylinder with a constant number of radial layers
 std::vector<double> CellPositionsHCalPhiThetaSegTool::calculateLayerRadiiBarrel() {
   return calculateLayerRadii(0, m_layersRetrieved->size());
 }
 
-// to be used for HCalThreePartsEndcap
+// calculateLayerRadiiEndcap should be used for HCalThreePartsEndcap which is formed
+// by three cylinders along the z-coordinate and each cylinder has a different number of radial layers
 std::vector<double> CellPositionsHCalPhiThetaSegTool::calculateLayerRadiiEndcap() {
   std::vector<double> radii;
 
-  // Calculate radii for each part and merge the results
+  // Calculate radii for each part (cylinder) and merge the results
   unsigned int upperIndexLayerRadiiPartOne = m_numLayersHCalThreeParts[0];
   unsigned int upperIndexLayerRadiiPartTwo = upperIndexLayerRadiiPartOne + m_numLayersHCalThreeParts[1];
 
diff --git a/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.h b/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.h
index 55f05937..369232a9 100644
--- a/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.h
+++ b/RecFCCeeCalorimeter/src/components/CellPositionsHCalPhiThetaSegTool.h
@@ -31,7 +31,14 @@ class Segmentation;
 }
 
 /** @class CellPositionsHCalPhiThetaSegTool
+ * 
+ *  Tool to determine each Calorimeter cell position.
  *
+ *  For the FCCee HCal Barrel and EndCap with phi-theta segmentation,
+ *  determined from the segmentation and the LayeredCalorimeterData extension.
+ *  The LayeredCalorimeterData extension is part of the geometry description.
+ * 
+ *  @author Michaela Mlynarikova
  */
 
 class CellPositionsHCalPhiThetaSegTool : public GaudiTool, virtual public ICellPositionsTool {
@@ -50,23 +57,27 @@ class CellPositionsHCalPhiThetaSegTool : public GaudiTool, virtual public ICellP
   virtual int layerId(const uint64_t& aCellId) final;
 
   virtual std::vector<double> calculateLayerRadii(unsigned int startIndex, unsigned int endIndex); 
+
   virtual std::vector<double> calculateLayerRadiiBarrel(); 
+
   virtual std::vector<double> calculateLayerRadiiEndcap(); 
 
 private:
   /// Pointer to the geometry service
   SmartIF<IGeoSvc> m_geoSvc;
-  /// Name of the calorimeter readout
+  /// Name of the hadronic calorimeter readout
   Gaudi::Property<std::string> m_readoutName{this, "readoutName", "HCalBarrelReadout"};
-  /// Name of the calorimeter 
+  /// Name of the hadronic calorimeter
   Gaudi::Property<std::string> m_detectorName{this, "detectorName", "HCalBarrel"};
-
+  /// Theta-phi segmentation
+  dd4hep::DDSegmentation::FCCSWGridPhiTheta_k4geo* m_segmentation = nullptr;
+  /// Cellid decoder
+  dd4hep::DDSegmentation::BitFieldCoder* m_decoder = nullptr;
+  /// vector to store calculated layer radii
   std::vector<double> m_radii;
-  dd4hep::DDSegmentation::FCCSWGridPhiTheta_k4geo* m_segmentation;
-  dd4hep::DDSegmentation::BitFieldCoder* m_decoder;
-  dd4hep::VolumeManager m_volman;
-  // layer radii calculated on the flight from the geometry 
-  const std::vector<dd4hep::rec::LayeredCalorimeterStruct::Layer>* m_layersRetrieved;
+  /// layers retrieved from the geometry
+  const std::vector<dd4hep::rec::LayeredCalorimeterStruct::Layer>* m_layersRetrieved = nullptr;
+  /// for the HCal Endcap, one needs to provide the number of layers in each cylinder
   Gaudi::Property<std::vector<int>> m_numLayersHCalThreeParts{this, "numLayersHCalThreeParts", {6,9,22}};
 };
 #endif /* RECCALORIMETER_CellPositionsHCalPhiThetaSegTool_H */
\ No newline at end of file