SIGIL: Compiling Agent Skills into Typed Harnesses
TL;DR
These results show that compiling procedural structure improves the reliability and efficiency of skill execution while retaining model judgment where it is needed, and shows that compiling procedural structure improves the reliability and efficiency of skill execution while retaining model judgment where it is needed.
Abstract
Agent skills provide a reusable way to specify multi-step agent behavior, but they remain natural-language specifications interpreted by the model at runtime. As a result, required tool calls, ordering constraints, and checks may be skipped even when explicitly prescribed by the skill. We introduce Skill Compilation, a paradigm that translates natural-language skills into executable agent programs while preserving model judgment where semantic decisions are required. We realize this idea in SIGIL. SIGIL extracts source-grounded requirements, decomposes them using a closed Agent Instruction Set (AIS), composes them into AG-IR with explicit ownership, data flow, and control flow, and deterministically lowers validated AG-IR into executable code. Across 33 publicly available SKILL.md files and three runtime models, SIGIL increases mean Applicable-Mandate Compliance (AMC), the fraction of applicable skill requirements satisfied during execution, from 66.0% with direct skill execution to 88.6%. SIGIL also reduces total runtime token consumption by 2.40-5.95x. These results show that compiling procedural structure improves the reliability and efficiency of skill execution while retaining model judgment where it is needed.