Wrapping every tool in a natural-language interface beat frontier models by 6% while cutting API cost 85%

arXiv 2609.01736·high signalXBlueskyLinkedInCopy link

HEART (arXiv 2609.01736, 2026-09-01) replaces rigid API-schema invocation with Tool Primitives, where each tool is wrapped in an LLM interface that resolves schemas and executes internally, so tools talk to each other in natural language instead of the agent brokering incompatible output types. It backs this with ToolFace, a repository of 25,519 functions retrieved on demand rather than enumerated in context, plus a Planner, Router, and Verifier. The framework beat SFT baselines by 10% on average and GPT-5.4, Claude-4.6-Sonnet, and Gemini-3.1-Pro by 6% across five benchmarks while cutting API cost up to 85%, and on 50 real-world tasks completed 84% against a 22% average for the three commercial models.