I posted this before, but I've refined it...When making tool holders, I use D2 and G2 to describe the extension (diameter and length).  ST is the gage-length which is just set to whatever the customer has...if needed.  D3 is always used to describe diamter of the main holder.

I rarely use any more parameters than this in my tool assembly.  If I use a special extension, I just add the information to the comment.

I have to describe my holders this way, because my VB script that creates my tool-list and holder lists automatically in the Catia drafting module pull the information directly from my processes.

But here's a cool thing to put in the pptable, if you want to see the info in the program or just post it this way to make a set-up sheet (post it this way by choosing SEQ1 or 2 on the toolchanges, then create a macro and use batch programs to automatically make a good instruction sheet/tool-holder list directly from the aptsource file...oh...I have those programs/macro's linked to my post processor...so one stop shopping for cheap!)  Change DISPLY to PPRINT if you have to...my post processor ignores all PPRINTS after the first cutter statement...the handy way to ignore all the excess BS put in there by catia if you have notes in any of the MO's.

/
*START_NC_INSTRUCTION                  NC_START_MACRO
*START_SEQUENCE
PARTNO %MFG_IDENTIFIER %MFG_PROGRAM_NAME
*END
*END
/
*START_NC_INSTRUCTION                  NC_TOOL_CHANGE
*START_SEQUENCE
$$SEQNO_1_TOOL_CHANGE_DEFAULT
TPRINT/%MFG_TOOL_NAME
LOAD/TOOL,%MFG_TOOL_NUMBER,LENGTH,%MFG_TL_SET_LGTH
COOLNT/ON
*END
*START_SEQUENCE
$$SEQ_NO_2_CUTTER_INFO
TPRINT/%MFG_TOOL_NAME
LOAD/TOOL,%MFG_TOOL_NUMBER,LENGTH,%MFG_TL_SET_LGTH
COOLNT/ON
DISPLY^^^^^^^TOOL_INFORMATION^^^^^^^^
DISPLYTOOL:%MFG_TOOL_NUMBER
DISPLY%MFG_TOOL_NAME
DISPLYDIAMETER:%MFG_NOMINAL_DIAM
DISPLYRADIUS:%MFG_CORNER_RAD
DISPLYMATERIAL:%MFG_TOOTH_MAT
DISPLYNUMBER_OF_FLUTES:%MFG_NB_OF_FLUTES
DISPLYLENGTH_OF_CUT:%MFG_CUT_LENGTH
DISPLYLENGTH_OUT_OF_HOLDER:%MFG_ASS_GAGE_1
DISPLYSHANK_DIAM:%MFG_BODY_DIAM
DISPLYCOMMENT:%MFG_TOOL_COMMENT
DISPLY^^^^^^HOLDER_INFORMATION^^^^^^^
DISPLYEXTENSION_DIAMETER:%MFG_DIAMETER_2
DISPLYEXTENSION_LENGTH:%MFG_ASS_GAGE_2
DISPLYHOLDER_DIAMETER:%MFG_DIAMETER_3
DISPLYLENGTH_FROM_GAGE:%MFG_TL_SET_LGTH
DISPLYCOMMENT:%MFG_ASS_COMMENT
*END
*START_SEQUENCE
$$SEQ_NO_3_DRILL_TOOL_INFO
TPRINT/%MFG_TOOL_NAME
LOAD/TOOL,%MFG_TOOL_NUMBER,LENGTH,%MFG_TL_SET_LGTH
COOLNT/ON
DISPLY^^^^^^^TOOL_INFORMATION^^^^^^^^
DISPLYTOOL:%MFG_TOOL_NUMBER
DISPLY%MFG_TOOL_NAME
DISPLYDIAMETER:%MFG_NOMINAL_DIAM
DISPLYMATERIAL:%MFG_TOOTH_MAT
DISPLYLENGTH_OF_CUT:%MFG_CUT_LENGTH
DISPLYLENGTH_OUT_OF_HOLDER:%MFG_ASS_GAGE_1
DISPLYTIP_ANGLE:%MFG_CUT_ANGLE
DISPLYSHANK_DIAM:%MFG_BODY_DIAM
DISPLYCOMMENT:%MFG_TOOL_COMMENT
DISPLY^^^^^^HOLDER_INFORMATION^^^^^^^
DISPLYEXTENSION_DIAMETER:%MFG_DIAMETER_2
DISPLYEXTENSION_LENGTH:%MFG_ASS_GAGE_2
DISPLYHOLDER_DIAMETER:%MFG_DIAMETER_3
DISPLYLENGTH_FROM_GAGE:%MFG_TL_SET_LGTH
DISPLYCOMMENT:%MFG_ASS_COMMENT
*END
*START_SEQUENCE
$$SEQ_NO_4_PROGRAM_STOP
TPRINT/%MFG_TOOL_NAME
LOAD/TOOL,%MFG_TOOL_NUMBER,LENGTH,%MFG_TL_SET_LGTH
STOP
DISPLYADD BOLTS
DISPLYREMOVE CLAMPS
COOLNT/ON
*END
*END
/