It is not an anticoagulant, quite the opposite actually. The blood (limulus amoebocyte lysate) will coagulate at the slightest hint of gram-negative bacteria and their endotoxins.
It's most likely a defense mechanism against bacterial infections.
It's widely used in medicine to check for bacterial contamination of injectable pharmaceuticals.
I love how every single source emphasizes it's "single-planet", just because it's by Hello Games.
Cause fantasy games with dragons are famously known to all contain interstellar travel.