Play2Prompt

Researchers from MIT CSAIL and IBM introduce Play2Prompt, a framework that empowers LLM agents to learn how to use external tools entirely in a zero-shot manner, without requiring labeled examples or high-quality documentation. Key innovations include: ● Tool "play" for usage discovery – Play2Prompt treats tools like black boxes and systematically plays with them (via trial-and-error API calls) to discover correct usage patterns. It reverse-engineers examples by first identifying working invocations, then generating a query-answer pair that fits the invocation and response. ● Two-stage optimization – The system iteratively builds: (1) tool-use demonstrations via self-reflective beam search and rejection sampling; and (2) refined tool documentation, using those examples as a validation set. This dual improvement allows LLMs to better understand and utilize unfamiliar APIs. ● Self-reflective beam search – Inspired by active learning, Play2Prompt favors hard examples that models initially fail on. These examples offer higher learning value and guide documentation improvements more effectively. ● Strong zero-shot performance – On BFCL Executable and StableToolBench, Play2Prompt yields consistent accuracy gains of +5–7% over baseline LLaMA and GPT-3.5 models and even boosts GPT-4o by up to +3.3%, particularly excelling in challenging multi-tool or REST call settings. ● Robust to poor documentation – Even when 50% of parameter descriptions are randomly dropped, Play2Prompt recovers and surpasses baseline performance, making it ideal for real-world tool integration with sparse or noisy metadata. ● Better than EasyTool – Unlike prior methods like EasyTool (which depend on labeled examples from related tools), Play2Prompt remains fully zero-shot and outperforms them in consistency, especially for models sensitive to instruction drift like GPT-4o.