diff --git a/qpms/qpms_types.h b/qpms/qpms_types.h
index 550d8bd..8b169b2 100644
--- a/qpms/qpms_types.h
+++ b/qpms/qpms_types.h
@@ -286,10 +286,18 @@ typedef struct qpms_irot3_t {
 typedef struct qpms_vswf_set_spec_t {
         size_t n; ///< Actual number of VSWF indices included in ilist.
         qpms_uvswfi_t *ilist; ///< List of wave indices.
-        qpms_l_t lMax; ///< Maximum degree of the waves specified in ilist.
-        qpms_l_t lMax_M, ///< Maximum degree of the magnetic (M-type) waves.
-                 lMax_N, ///< Maximum degree of the electric (N-type) waves.
-                 lMax_L; ///< Maximum degree of the longitudinal (L-type) waves.
+	/// Maximum degree of the waves specified in ilist overall.
+	/** `max(lMax_M, lMax_N, lMax_L)` */
+        qpms_l_t lMax; 
+	/// Maximum degree of the magnetic (M-type) waves. 
+	/** Set to 0 if no magnetic waves present. */
+        qpms_l_t lMax_M, 
+	/// Maximum degree of the electric (N-type) waves. 
+	/** Set to 0 if no electric waves present. */
+                 lMax_N,
+	/// Maximum degree of the longitudinal (L-type) waves. 
+	/** Set to -1 if no longitudinal waves present. */
+                 lMax_L;
         size_t capacity; ///< Allocated capacity of ilist.
         qpms_normalisation_t norm; ///< Normalisation convention. To be set manually if needed.
 } qpms_vswf_set_spec_t;
diff --git a/qpms/vswf.h b/qpms/vswf.h
index 90ac7a5..33dae0e 100644
--- a/qpms/vswf.h
+++ b/qpms/vswf.h
@@ -207,7 +207,16 @@ qpms_errno_t qpms_vswf_fill_csph(
 	csph_t kdrj, //< VSWF evaluation point.
 	qpms_bessel_t btyp, qpms_normalisation_t norm);
 
-qpms_errno_t qpms_vecspharm_fill(csphvec_t *const a1target, csphvec_t *const a2target, csphvec_t *const a3target,
+/// Evaluate vector spherical harmonics at \a dir.
+/**
+ * The length of each of the target arrays shall be `lMax * (lMax + 2)`.
+ * If any of the target arrays pointers is NULL, the corresponding VSH will not be evaluated.
+ * The "zeroth" radial VSH \f$ \vshrad_0^0 \f$ is not evaluated.
+ */
+qpms_errno_t qpms_vecspharm_fill(
+		csphvec_t *const a1target, ///< Target array for radial VSH \f$ \vshrad \f$.
+	       	csphvec_t *const a2target, ///< Target array for "rotational" VSH \f$ \vshrot \f$.
+	       	csphvec_t *const a3target, ///< Target array for "gradiental" VSH \f$ \vshgrad \f$.
 		qpms_l_t lMax, sph_t dir, qpms_normalisation_t norm);
 qpms_errno_t qpms_vecspharm_dual_fill(csphvec_t *const a1target, csphvec_t *const a2target, csphvec_t *const a3target,
 		qpms_l_t lMax, sph_t dir, qpms_normalisation_t norm);