Hidden APM modes

In running a debug trace for APM, I see the following HTTP headers as being interrogated. What are they used for? I am familiar with clientless-mode but I'm not sure what the other ones are for.

Version 11.5.1 HF5

Nov 26 15:06:30 BIGIP-1 debug apd[7805]: 01490000:7: AccessPolicyD.cpp func: "process_request()" line: 670 Msg: request-from: ""
Nov 26 15:06:30 BIGIP-1 debug apd[7805]: 01490000:7: AccessPolicyD.cpp func: "process_request()" line: 672 Msg: clientless-mode: ""
Nov 26 15:06:30 BIGIP-1 debug apd[7805]: 01490000:7: AccessPolicyD.cpp func: "process_request()" line: 674 Msg: no-inspection-host-mode: ""