Looks like a Mithraculus species. Which one I don't know. Are the claws flat on the tips? If it is a Mithraculus species, it will eat mainly on algae but they are opportunistic feeders so keep an eye on it. When my algae was running low I fed them pieces of nori.
I'd remove the little guy. I've had several that look the same and most were harmless. Then there was one that seemed to damage my coral.
When in doubt kill it!