Simon Willison’s Weblog

11th April 2025 - Link Blog

llm-fragments-rust (via) Inspired by Filippo Valsorda's llm-fragments-go, Francois Garillot created llm-fragments-rust, an LLM fragments plugin that lets you pull documentation for any Rust crate directly into a prompt to LLM.

I really like this example, which uses two fragments to load documentation for two crates at once:

llm -f rust:rand@0.8.5 -f rust:tokio "How do I generate random numbers asynchronously?"

The code uses some neat tricks: it creates a new Rust project in a temporary directory (similar to how llm-fragments-go works), adds the crates and uses cargo doc --no-deps --document-private-items to generate documentation. Then it runs cargo tree --edges features to add dependency information, and cargo metadata --format-version=1 to include additional metadata about the crate.