UPDATED TO VERSION 1.1
The program has been updated to Version 1.1 instead of comparing two tile_config.json files it now compares the tile set's tile_config.json file with all .json files located in data\json and data\json\items. This should provide better functionality, as well as make sure every single item id is accounted for.
(Version 1.1.1 released November 10, Fixed a bug where vehicle parts were not accurately checked. Reupped link)
I made this tool thanks to an idea from Natures Witness as a tool for tile set makers. What this program does is it looks at your tile set, and tells you what item id's you are missing from your tile set. This will allow you to quickly update your tile sets as the game updates and new items are added. The program was coded in C# using the .Net 4.0 framework. If request is there, I could maybe rewrite this as a command-line based python program to allow for cross-platform compatibility. Download Here!
Use of this program is simple. Run the program. Select your tile set's tile_config.json and point the program to your data/json folder. Click check and the program will scan all relevant json files and create a "missing.txt" file for you. I believe I have it checking all relevant json files, but let me know if I missed one!
Here is a list of all files I check (and they are checked in order and written in order on missing.txt if it help you at all)
Let me know if any bugs arise, or if there is any requested functionality.