LAPIS: Lightweight API Specification for Intelligent Systems

Abstract

New API specification format designed for LLMs. Reduces token overhead by 85.5% compared to OpenAPI YAML and 88.6% compared to OpenAPI JSON, with results validated on GitHub, Twilio and DigitalOcean APIs.

OpenAPI was designed for code generators and documentation tools. When an LLM processes it, it spends tokens on information the model doesn’t need.

LAPIS is an API specification format designed specifically for how language models consume documentation. Tested on GitHub, Twilio and DigitalOcean APIs, the average reduction is 85.5% fewer tokens compared to OpenAPI YAML and 88.6% compared to JSON.

Beyond compactness, LAPIS includes centralized error handling, webhook triggers, rate limiting descriptions and operation flows, things OpenAPI scatters or doesn’t address directly.

It converts automatically from OpenAPI 3.x. The specification is open under CC BY 4.0.