diff --git a/include/scalfmm/operators/fmm_operators.hpp b/include/scalfmm/operators/fmm_operators.hpp
index 0f626e6182a38eaba20da989b34161f3922dd6a6..12c96e26e667e275c31d0375e60f75eb2fecec7b 100644
--- a/include/scalfmm/operators/fmm_operators.hpp
+++ b/include/scalfmm/operators/fmm_operators.hpp
@@ -120,7 +120,7 @@ namespace scalfmm::operators
         auto matrix_kernel() const -> matrix_kernel_type const& { return m_matrix_kernel; }
 
         /**
-         * @brief
+         * @brief Get the matrix kernel 
          *
          * @return matrix_kernel_type&
          */
@@ -157,23 +157,12 @@ namespace scalfmm::operators
         auto mutual() -> bool& { return m_mutual; }
 
       private:
-        /**
-         * @brief The matrix kernel used in the near field.
-         *
-         */
-        matrix_kernel_type m_matrix_kernel;
+        matrix_kernel_type m_matrix_kernel;   ///< he matrix kernel used in the near field.
 
-        /**
-         * @brief The separation criterion used in the near field.
-         *
-         */
-        int m_separation_criterion{matrix_kernel_type::separation_criterion};
+        int m_separation_criterion{
+          matrix_kernel_type::separation_criterion};   ///< The separation criterion used in the near field.
 
-        /**
-         * @brief To specify if we use symmetric algorithm for the p2p (mutual interactions).
-         *
-         */
-        bool m_mutual{true};
+        bool m_mutual{true};   ///< To specify if we use symmetric algorithm for the p2p (mutual interactions).
     };
 
     /**
@@ -200,7 +189,7 @@ namespace scalfmm::operators
       public:
         using approximation_type = ApproximationType;
         static constexpr bool compute_gradient = ComputeGradient;
-        // precise the homogeneous type of the kernel
+        ///<  precise the homogeneous type of the kernel
         static constexpr auto homogeneity_tag = approximation_type::homogeneity_tag;
 
         /**
@@ -269,17 +258,9 @@ namespace scalfmm::operators
       private:
         // Here, be careful with this reference with the lifetime of matrix_kernel.
 
-        /**
-         * @brief the approximation method used in the near field.
-         *
-         */
-        approximation_type const& m_approximation;
+        approximation_type const& m_approximation;   ///<  the approximation method used in the near field.
 
-        /**
-         * @brief
-         *
-         */
-        int m_separation_criterion{approximation_type::separation_criterion};
+        int m_separation_criterion{approximation_type::separation_criterion};   ///<  the separation criterion.
     };
 
     /**
@@ -376,31 +357,23 @@ namespace scalfmm::operators
         }
 
         /**
-         * @brief
+         * @brief  get the near field of the FMM operator
          *
          * @return near_field_type const&
          */
         auto near_field() const -> near_field_type const& { return m_near_field; }
 
         /**
-         * @brief
+         * @brief get the far field of the FMM operator
          *
          * @return far_field_type const&
          */
         auto far_field() const -> far_field_type const& { return m_far_field; }
 
       private:
-        /**
-         * @brief the near field used in the fmm operator.
-         *
-         */
-        near_field_type const& m_near_field;
+        near_field_type const& m_near_field;   ///< the near field used in the fmm operator.
 
-        /**
-         * @brief the far field used in the fmm operator.
-         *
-         */
-        far_field_type const& m_far_field;
+        far_field_type const& m_far_field;   ///< the far field used in the fmm operator.
     };
 
 }   // namespace scalfmm::operators