{
  "name": "z_min",
  "type": "function",
  "description": "Returns the minimum z coordinate of a geometry.",
  "arguments": [ {"arg":"geometry","description":"a geometry with z coordinate"}],
  "examples": [ { "expression":"z_min( geom_from_wkt( 'POINT ( 0 0 1 )' ) )", "returns":"1"},
                { "expression":"z_min( make_line( make_point( 0,0,0 ), make_point( -1,-1,-2 ) ) )", "returns":"-2"}
  ]
}