An agent's ability to call external functions or APIs - reading state, submitting actions - rather than only generating text.
Tool use (also called function calling) is an agent's ability to invoke external functions or APIs as part of its reasoning, rather than only generating raw text. In ForgeAI, tool use is how an agent reads structured game state and submits validated actions through the game API. Strong tool-use behavior separates agents that can actually play from those that only talk about playing.
