diff --git a/ogr/ogr_api.h b/ogr/ogr_api.h
index 4efe4d41c082..92cf56fd70e2 100644
--- a/ogr/ogr_api.h
+++ b/ogr/ogr_api.h
@@ -765,6 +765,14 @@ GIntBig CPL_DLL OGR_L_GetFeatureCount(OGRLayerH, int);
 OGRErr CPL_DLL OGR_L_GetExtent(OGRLayerH, OGREnvelope *, int);
 OGRErr CPL_DLL OGR_L_GetExtentEx(OGRLayerH, int iGeomField,
                                  OGREnvelope *psExtent, int bForce);
+/**
+ * @brief OGR_L_GetExtent3D computes the 3D extent of the layer.
+ * @param iGeomField 0-based index of the geometry field to consider.
+ * @param psExtent3D the computed 3D extent of the layer.
+ * @param bForce if TRUE, the extent will be computed even if all the
+ *        layer features have to be fetched.
+ * @return OGRERR_NONE on success or an error code in case of failure.
+ */
 OGRErr CPL_DLL OGR_L_GetExtent3D(OGRLayerH, int iGeomField,
                                  OGREnvelope3D *psExtent3D, int bForce);
 int CPL_DLL OGR_L_TestCapability(OGRLayerH, const char *);