A standard USB jack has 4 pins. A micro USB jack has 5 pins. The extra pin is for OTG auto-detect, which is signaled by jumpering two pins together inside the host mode adapter. Some adapter cables are missing that jumper, so need software switching between device mode and host mode.
Because the pins are so small, it would be hard to check for that jumpered connection unless you had a breakout adapter that brings the pins out where you can connect to them and measure their resistance. In my case, I would check an OTG host mode adapter by plugging USB flash memory stick into it and into my Nexus 7, and see if my USB StickMount program detects it. That is how I know that some of my cables autodetect and others do not (depending on which ebay store supplied them).