diff --git a/Set_movable_separability_2/include/CGAL/top_edge_single_mold_translational_casting_2.h b/Set_movable_separability_2/include/CGAL/top_edge_single_mold_translational_casting_2.h
index 87052197333..006361b394f 100644
--- a/Set_movable_separability_2/include/CGAL/top_edge_single_mold_translational_casting_2.h
+++ b/Set_movable_separability_2/include/CGAL/top_edge_single_mold_translational_casting_2.h
@@ -24,6 +24,27 @@ namespace CGAL {
 
 namespace Set_movable_separability_2 {
 
+/*! Given a simple polygon and an edge of the polygon, this function determines
+ * whether a cavity (of a mold in the plane) that has the shape of the polygon
+ * can be used so that the polygon could be casted in the mold with the input
+ * edge being the top edge and then pulled out of the mold without colliding
+ * into the mold (but possibly sliding along the mold surface). If the polygon
+ * is <em>castable</em> this way, the function computes the closed range of pull
+ * directions asuming that the the top edge normal is parallel to the
+ * \f$y\f$-axis. In other words, every direction in the range (if exists) must
+ * have a positive component in the positive \f$y\f$-direction.
+ *
+ * \param[in] pgn the input polygon.
+ * \param[in] i the index of an edge in pgn.
+ * \return a pair of elements, where the first is a Boolean that indicates
+ *         whether the input edge is a valid top edge, and the second
+ *         is a closed range of pull-out directions represented as a pair
+ *         of the extreme directions in the range. If the input edge is not
+ *         a valid top edge, the range is nondeterministic.
+ *
+ * \pre `png` must be non-degenerate (has at least 3 vertices), simple, and
+ * does not have three consecutive collinear vertices.
+ */
 template <typename CastingTraits_2>
 std::pair<bool, std::pair<typename CastingTraits_2::Direction_2,
                           typename CastingTraits_2::Direction_2> >
@@ -38,6 +59,11 @@ top_edge_single_mold_translational_casting_2
 template <typename CastingTraits_2>
 std::pair<bool, std::pair<typename CastingTraits_2::Direction_2,
                           typename CastingTraits_2::Direction_2> >
+/*! Same as above with the additional traits argument.
+ * \param[in] pgn the input polygon.
+ * \param[in] i the index of an edge in pgn.
+ * \param[in] traits the traits to use.
+ */
 top_edge_single_mold_translational_casting_2
 (const CGAL::Polygon_2<CastingTraits_2>& pgn, size_t i)
 {