  Planning has been part of the core pursuit for artificial intelligence since
its conception, but earlier AI agents mostly focused on constrained settings
because many of the cognitive substrates necessary for human-level planning
have been lacking. Recently, language agents powered by large language models
(LLMs) have shown interesting capabilities such as tool use and reasoning. Are
these language agents capable of planning in more complex settings that are out
of the reach of prior AI agents? To advance this investigation, we propose
TravelPlanner, a new planning benchmark that focuses on travel planning, a
common real-world planning scenario. It provides a rich sandbox environment,
various tools for accessing nearly four million data records, and 1,225
meticulously curated planning intents and reference plans. Comprehensive
evaluations show that the current language agents are not yet capable of
handling such complex planning tasks-even GPT-4 only achieves a success rate of
0.6%. Language agents struggle to stay on task, use the right tools to collect
information, or keep track of multiple constraints. However, we note that the
mere possibility for language agents to tackle such a complex problem is in
itself non-trivial progress. TravelPlanner provides a challenging yet
meaningful testbed for future language agents.
