cargo-brief

Visibility-aware Rust API extractor — pseudo-Rust output for AI agent consumption.

Why?

AI coding agents need to understand crate APIs without reading full source files. HTML docs waste tokens on navigation chrome, and cargo doc --json is too verbose. cargo-brief outputs concise pseudo-Rust that fits in a context window:

• Function bodies replaced with ;
• Only items visible from the caller's perspective
• Doc comments preserved verbatim
• Compact module hierarchy

Installation

cargo install cargo-brief

Requires the nightly toolchain (for rustdoc --output-format json):

rustup toolchain install nightly

Usage

cargo brief [GLOBAL FLAGS] <subcommand> [ARGS...] [OPTIONS...]

Global flags (-C, -F, --no-cache, …) must appear before the subcommand name.

Subcommands

Run cargo brief <subcommand> --help for full options.

Core Subcommands

api — render a crate's API

# Current package (run inside a Cargo project)
cargo brief api

# Specific module
cargo brief api self::net::tcp

# Recurse all submodules
cargo brief api self --recursive

# Limit depth
cargo brief api self --depth 2

# Exclude item kinds
cargo brief api self --no-macros --no-traits

# Compact output (no doc comments, collapsed bodies)
cargo brief api self --compact

# Show only what's visible from an external caller
cargo brief api my-crate --at-package consumer-crate

Target resolution — the [TARGET] argument accepts:

search — find items by name

# Substring search (smart-case: all-lowercase = insensitive)
cargo brief search self spawn

# Multiple patterns are AND-matched
cargo brief search self "spawn async"

# Show methods/fields of a type
cargo brief search self --methods-of Handle

# OR-match with comma
cargo brief search self "EventReader,EventWriter"

# Glob and exact-match operators
cargo brief search self "Shader*Ref"
cargo brief search self "=Router"

Pattern DSL: space = AND, comma = OR. Operators per token:

• word — substring match
• w*ld — glob (* = 0+ chars, ? = 1 char)
• =Name — exact final segment
• -term — exclude (use -- for patterns starting with -)

summary — module overview

cargo brief summary self
cargo brief summary self::net

One line per module showing counts of traits, structs, enums, functions, types, constants, macros, and unions.

Remote Crates (-C)

Pass -C before the subcommand to treat TARGET as a crates.io spec:

# Overview of a crates.io package
cargo brief -C summary tokio@1

# Browse a module
cargo brief -C api tokio@1 net

# Search
cargo brief -C search serde@1 Serialize

# Feature-gated APIs (omit -F and items are invisible)
cargo brief -C -F rt,net api tokio@1 --compact

Crate spec syntax: name (latest), name@1 (semver-compatible), name@1.2.3 (exact pin). Downloaded crates are cached at ~/.cache/cargo-brief/crates/. Run cargo brief clean to clear.

Output Format

// crate my_crate
mod utils {
    /// Computes the hash of the input.
    pub fn hash(input: &[u8]) -> u64;

    pub struct Config {
        pub timeout: Duration,
        pub retries: u32,
        // ... private fields
    }

    impl Config {
        pub fn new() -> Self;
        pub fn with_timeout(self, timeout: Duration) -> Self;
    }

    pub trait Processor: Send + Sync {
        type Output;
        fn process(&self, input: &[u8]) -> Self::Output;
    }
}

AI Agent Setup

Claude Code

Add to your project's CLAUDE.md:

## Exploring Crate APIs

Use `cargo brief` to inspect crate interfaces instead of reading source files directly.

# Typical workflow
cargo brief summary self                     # overview of modules
cargo brief api self::some_module            # drill into a module
cargo brief search self SomeType --members   # find a specific item
cargo brief code fn some_function --refs     # read source + references

# Named workspace crate
cargo brief api my-crate --recursive

# External visibility only
cargo brief api my-crate --at-package consumer-crate

# Remote crate from crates.io
cargo brief -C summary tokio@1
cargo brief -C search serde@1 Deserialize

# Specify manifest when outside the workspace root
cargo brief api self --manifest-path path/to/Cargo.toml

Generic LLM Agent

cargo brief api self --recursive | your-agent-tool
cargo brief api self::network::http | your-agent-tool

License

MPL-2.0