What is this tool for and how can I clean my faucet spray head?

I have a Kraus Geo Axis KPF-1750 kitchen faucet. The flow has become very low (it was fine yesterday). I took out the installation guide that came with the package and found a red plastic tool in the same bag. It seems to fit the filter on the spray head but I am not sure what it is for. More importantly, how should I clean the faucet spray head?

Well apparently, with what appears to be a recessed aerator, that tool is required to remove it.
Did you try removing the aerator and flushing it clean? If it appears to have a buildup of minerals and such, you can soak it in vinegar for awhile then flush it again.

When you remove it, take careful note of any pieces that are removable from the aerator assembly(if that's the case. It may not be.) so you can put it back as it was.

I see that this company has terrible documentation regarding care and maintenance.

When you say, "how should I clean the faucet spray head?", what specifically are you referring to?

Thanks for the reply. I figured out what the tool was for. However, I can't seem to remove the aerator with this tool. In fact, I think I may have already stripped the teeth, so I probably need to stop by my local hardware store to get a new one. In the meantime I'll try the vinegar method you suggested.

About the spray head cleaning question, let me show you the spray head overall construction:



and this is the bottom view:



I can remove the allen set screw, but the black plastic piece won't come out. If I buy a new aerator removal tool and get the aerator out, is there a way to clean inside the spray head? The faucet worked fine until yesterday evening. The problem is the flow rate is low now, so I assume something must clog up the spray head.

Either the aerator, flow restrictor, or check valve is clogged up, or all three might be.

They are all designed to be flushed out, or replaced if they are hopelessly clogged.
The manufacturer should be able to send or sell you new pieces.

I doubt you will find a matching aerator removal tool at a hardware store, but fingers crossed.
Maybe you are twisting it the wrong way?

The check valve might be at the end of the hose under the sink, or could be at the spray head end.

Look for videos on Youtube that will show your brand of faucet being cleaned out.

See if you can pull out that light blue plastic piece.
Try a needle nose pliers, or flat screwdriver, or anything that can hook it and pull it out.
There might also be another piece behind it that comes out.

Jeff, thanks for the reply. You were right I weren't able to find a matching aerator or the tool from Home Depot or Lowe's. I did end up calling Kraus and I was pleasantly surprised they were going to send me a new spray head for free even though the faucet was out of warranty.

Once I have the new head, I'll play with the old one. Maybe I can get myself a spare in case this happens again. If I remove the spray head, the flow is normal coming out of the hose, therefore I am guessing the check valve is probably okay.

I hope you asked then to send another tool to remove the old aerator. Made of metal since that old aerator was so tight it broke the first one.

Remind me again, do not buy a faucet with a pull-out spray aerator, ....except when I'm looking to sell my house. Buyers love them initially, then their Plumbers love 'em - for the income they generate.
Lovely items consistently develop problems; mineral build-up, and diverter valve failure are the most common, but, I've seen the flexible hose fail, which can really ruin your day, and your kitchen. Fashion, it's a wonderful thing

I have the same removal tool for mine but mine comes out easily. I think the key is to exercise the aerator maybe 1/4ly.