I wish I had time to clean up and release my private copy of IrTool.exe. It displays more of the output from DecodeIR.dll than the available version.

DecodeIR generates "T=1" or "T=0" for RC5 codes to tell you the state of the "toggle bit".

Several protocols, including RC5, have a toggle bit that changes state with each press, so when you press the same key multiple times it alterantes between two different signals. That way the receiving device can reliably distinguish a long press of a button vs. two shorter presses of the same button with very little time between.

If you have an RC5 signal in 0000 format in a CCF file and run it through DecodeCCF.exe, you will get that info from DecodeIR. But the available IRTool.exe ignores that part of the DecodeIR results. If you paste a clean sample of RC5 in 0000 format into most versions of ProntoEdit, it will get immediately converted to 5000 format. In that format the single Pronto Hex string represents both toggle bit states, so DecodeCCF won't display any "T=". So with present tools you only see the "T=0" or "T=1" when decoding a signal in a CCF that wasn't recognised and converted.