00 Agent is the hardest of the three difficulty settings in GoldenEye 007. Enemies are more accurate and do more damage, and Body Armor is less abundant. On most levels, players must also complete more objectives than in Agent or Secret Agent.
The main practical consequence of this is that world record times on 00A are longer than for lower difficulty settings. In addition, different techniques must be employed to stay alive - an area which you could ordinarily run through on Agent may become a deathtrap on 00A which must be taken carefully, or a player may find himself spending time going out of his way to get Body Armor when ordinarily it would not be needed.