inSlope() → double
Returns the slope entering the keyframe.
This method raises hou.KeyframeValueNotSet if the slope has not been set or the slope is tied.

I'm trying to get the inSlope value of a freshly/recently created keyframe, but it won't let me check it unless I untie it.
hou.Keyframe [www.sidefx.com]

It honestly just seems impossible. Does anyone know how to achieve this? Even with hscript, anything.

In a classic fashion I think I found the answer 10 minutes after posting this thread.

Hscript chkeyget [www.sidefx.com] can seemingly provide information about slopes and accel on tied keyframes. After a few initial tests, the values seem to match what I see in the GUI.

Edit: God, I'm dense. When handles are tied, inSlope is the same as out slope. No hscript needed.