This is a set of recommendations on how to design and present APIs for the Rust programming language. They are authored largely by the Rust library team, based on experiences building the Rust standard library and other crates in the Rust ecosystem.
These are only guidelines, some more firm than others. In some cases they are vague and still in development. Rust crate authors should consider them as a set of important considerations in the development of idiomatic and interoperable Rust libraries, to use as they see fit. These guidelines should not in any way be considered a mandate that crate authors must follow, though they may find that crates that conform well to these guidelines integrate better with the existing crate ecosystem than those that do not.
This book is organized in two parts: the concise checklist of all individual guidelines, suitable for quick scanning during crate reviews; and topical chapters containing explanations of the guidelines in detail.