If you're building anything with Apple's on-device 3B parameter LLM that shipped at WWDC 2025, this is your complete API reference in skill form. It covers the entire Foundation Models framework with all the code examples from the sessions. The real value is having the specs and limitations right there while you work: 4096 token context window, 2-bit quantized, good for summarization and classification but explicitly not for math or world knowledge. Saves you from constantly switching to documentation tabs when you're trying to figure out what this thing can actually handle on an iPhone.
npx skills add https://github.com/charleswiltgen/axiom --skill axiom-foundation-models-ref