A tool AI is a type of Artificial Intelligence which is built to be used as a tool by the creators, rather than being an agent with its own action and goal-seeking behavior.
Generally meant to refer to AGI, tool AI is a proposed method for gaining some of the benefits of the intelligence while avoiding the dangers of having it act autonomously. It was coined by Holden Karnofsky, co-founder of GiveWell, in a critique of the Singularity Institute. Karnofsky proposed that, while he agreed that agent-based AGI was dangerous, it was an unnecessary path of development. His example of tool AI behavior was Google Maps, which uses complex algorithms and data to plot a route, but presents these results to the user instead of driving the user itself.
Eliezer Yudkowsky responded to this by enumerating several ways in which tool AI had similar difficulties in technical specification and safety. He also pointed out that it was not a common proposal among leading AGI thinkers.