Editing tool table in program

Am I out of my mind or is there a way to write an entry into the tool table via a running program?

I thought I saw a way to edit the tool table via code, but I cannot find it now.

I want to be able to write and re-write a single entry dynamically.

G10 L1 P... Lets you change the settings in the tool table, but it can't create a new entry.
linuxcnc.org/docs/2.6/html/gcode/gcode.html#sec:G10-L1_