से: Agent ~> Instrument
In causative verb constructions, we treat the "instrument" as an Agent onto itself since it is the one doing what the verb is.
Why is this a full Agent? This is very much provisional and subject to change. First of all, the function is undoubtedly Instrument. The problem is that instrumental agent does not perform the action with volition.
There was some discussion of making an Initiator-Executor distinction between the Agent↝Agent and the Agent↝Instrument. I am against this because it encodes volition into the scene role. This introduces all sorts of problems with modal constructions that don't use any one postposition consistently to refer to the same person: e.g. मैंने किया vs. मुझसे किया गया vs. मुझको करना था all are various forms of "I did it" but with different case markers on I. These all should get the same scene role.