QGIS/resources/function_help/json/point_n

{
  "name": "point_n",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Returns a specific node from a geometry.",
  "arguments": [{
    "arg": "geometry",
    "description": "geometry object"
  }, {
    "arg": "index",
    "description": "index of node to return, where 1 is the first node; if the value is negative, the selected vertex index will be its total count minus the absolute value"
  }],
  "examples": [{
    "expression": "geom_to_wkt(point_n(geom_from_wkt('POLYGON((0 0, 4 0, 4 2, 0 2, 0 0))'),2))",
    "returns": "'Point (4 0)'"
  }],
  "tags": ["specific", "node", "vertex"]
}