I've pasted an example of the exported map file format; the format is also specified in the manual (for readability I've run the JSON through a prettifier, Tilekit exports it to a compact format):

{
  "map": {
    "tile_w": 8,
    "tile_h": 8,
    "tile_spacing": 0,
    "image_filename": "../platformer.png",
    "animations": [
      {
        "idx": 51,
        "rate": 126,
        "frames": [
          51,
          59,
          60
        ]
      },
      {
        "idx": 6,
        "rate": 203,
        "frames": [
          6,
          22,
          41
        ]
      }
    ],
    "tags": [
      {
        "label": "testtag",
        "tiles": [
          1,
          5,
          6,
          22
        ]
      },
      {
        "label": "testtag2",
        "tiles": [
          25,
          17
        ]
      }
    ],
    "w": 16,
    "h": 16,
    "data": [
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 3, 44, 44, 9, 10, 61, 29, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 46, 56, 0, 0, 31, 9, 10, 10, 0, 0, 0,
      0, 0, 0, 0, 43, 31, 38, 33, 0, 31, 0, 0, 0, 34, 33, 0,
      0, 0, 0, 3, 44, 0, 2, 2, 11, 31, 0, 0, 11, 44, 2, 4,
      0, 0, 3, 44, 54, 0, 0, 56, 0, 0, 0, 0, 0, 46, 47, 0,
      0, 0, 28, 31, 25, 46, 47, 36, 0, 0, 0, 0, 8, 46, 56, 0,
      0, 3, 44, 47, 25, 46, 0, 2, 15, 15, 15, 15, 15, 31, 19, 0,
      0, 0, 53, 0, 55, 0, 0, 47, 24, 24, 0, 23, 55, 47, 34, 43,
      0, 0, 37, 53, 54, 0, 0, 0, 55, 55, 55, 55, 56, 37, 44, 44,
      0, 0, 0, 26, 37, 53, 54, 54, 54, 0, 54, 56, 19, 0, 46, 47,
      0, 0, 0, 27, 0, 26, 0, 0, 0, 31, 38, 0, 0, 0, 46, 56,
      0, 0, 0, 0, 0, 27, 0, 0, 0, 0, 10, 10, 10, 11, 31, 38
    ]
  },
  "objects": [
    {
      "name": "Player",
      "id": "$1",
      "x": "40",
      "y": "24",
      "w": "8",
      "h": "8",
      "color": "#493cdb"
    },
    {
      "name": "Chest",
      "id": "$2",
      "x": "104",
      "y": "48",
      "w": "8",
      "h": "8",
      "color": "#ff7f00"
    }
  ]
}

Exporting the ruleset to a lua module (such that you would define your rules in Tilekit and have your game do the auto tiling itself) looks as follows:

local function random(n) return math.random(n) - 1 end
local function chance(n, x, y) return random(100, x, y) < n end
local function get_tile(m, x, y)
  if x < 0 or x >= m.w or y < 0 or y >= m.h then return 0 end
  return m.data[x + y * m.w + 1]
end
local function process_tile(m, x, y)
if get_tile(m, x + 0, y + 0) == 0 and get_tile(m, x + 0, y + 1) == 0 
and get_tile(m, x + 0, y + 2) == 1 and get_tile(m, x + 1, y + 0) == 0 
and get_tile(m, x + -1, y + 0) == 0 and chance(3, x, y) then
return 51
end
if get_tile(m, x + 0, y + 0) == 0 and get_tile(m, x + 0, y + 1) == 1 
and chance(2, x, y) then
return 73
end
if get_tile(m, x + 0, y + 0) == 0 and get_tile(m, x + 0, y + 1) == 1 
and chance(4, x, y) then
return 43
end
if get_tile(m, x + 0, y + -1) == 19 and get_tile(m, x + 0, y + 0) == 5 then
return 48
end
if get_tile(m, x + 0, y + 0) == 19 and get_tile(m, x + 0, y + 1) ~= 19 then
return 6
end
if get_tile(m, x + 0, y + 0) == 19 then
return 5
end
if get_tile(m, x + 0, y + 0) == 0 and get_tile(m, x + 1, y + 0) == 1 
and get_tile(m, x + 0, y + 1) == 5 and chance(47, x, y) then
return 8
end
if get_tile(m, x + 0, y + 0) == 0 and get_tile(m, x + -1, y + 0) == 1 
and get_tile(m, x + 0, y + 1) == 5 and chance(77, x, y) then
return 7
end
if get_tile(m, x + 0, y + 0) == 5 and get_tile(m, x + 0, y + -1) == 0 then
return 15
end
if get_tile(m, x + 0, y + 0) == 5 and get_tile(m, x + 0, y + 1) == 1 
and chance(87, x, y) then
local n = random(3, x, y)
if n == 0 then
return 23
end
if n == 1 then
return 16
end
if n == 2 then
return 24
end
end
if get_tile(m, x + 0, y + 0) == 5 and chance(22, x, y) then
local n = random(2, x, y)
if n == 0 then
return 32
end
if n == 1 then
return 24
end
end
return 0
end
return function(src)
  local res = { w = src.w, h = src.h, data = {} }
  for y = 0, src.h - 1 do
    for x = 0, src.w - 1 do
      res.data[x + y * src.w + 1] = process_tile(src, x, y)
    end
  end
  return res
end