ferrisfetch

README

rsdoc

Semantic search for Rust crate documentation. Fetches rustdoc JSON from docs.rs, parses it into markdown, vectorizes it with Voyage AI, and stores everything in SQLite with HNSW indexing.

Features

• Semantic Search: Find documentation using natural language queries
• Content-Addressable Storage: Deduplicates docs across crate versions — re-indexing identical docs costs zero API calls
• Auto-Fetch on Read: Request docs for a crate you haven't indexed yet and it fetches automatically
• Re-export Resolution: Follows pub use chains to find canonical documentation
• crates.io Search: Search for crates by name or keyword
• Background Daemon: Heavy work runs in a background daemon that auto-exits after inactivity

Quick Start

Prerequisites

• Go 1.24+
• A Voyage AI API key

Installation

Build from Source

git clone https://github.com/jcdickinson/ferrisfetch
cd ferrisfetch
go build -o rsdoc ./cmd/rsdoc

Nix

nix run github:jcdickinson/ferrisfetch
nix profile install github:jcdickinson/ferrisfetch

Configuration

Create ~/.config/ferrisfetch/config.toml:

[voyage_ai]
model = "voyage-3.5"
rerank_model = "rerank-lite-1"

# Read API key from a file (recommended)
api_key = { path = "~/.config/ferrisfetch/voyage_api_key.txt" }
# Or inline (not recommended)
# api_key = "your-api-key"

Or use environment variables:

export FERRISFETCH_VOYAGE_AI_API_KEY="your-api-key"

Usage

When CLAUDECODE=1 or AGENT=1 is set, rsdoc --help outputs markdown instructions tailored for AI agents. To make an agent aware of the tool, add a CLI Tools section to your CLAUDE.md or AGENTS.md:

## CLI Tools

These tools are intended to be used in the same way that MCPs are. stderr is for logging and you should typically ignore it.

- `rsdoc --help`: used to search for crates, as well as semantic search across indexed crates. Use this instead of fetching documentation from doc.rs.

CLI tools typically use fewer tokens than MCPs.

Commands

rsdoc add serde tokio            # Index crates (latest version)
rsdoc add tokio@1.44.2           # Index a specific version
rsdoc search "async runtime"     # Semantic search
rsdoc search-crates serde        # Search crates.io
rsdoc get serde/latest/serde::Serialize  # Read a doc item (rsdoc:// prefix optional)
rsdoc status                     # Show indexed crates
rsdoc logs                       # Tail daemon log
rsdoc stop                       # Stop the daemon
rsdoc clear-cache                # Clear version resolution cache

Use --debug to run the daemon in-process with visible log output.

Architecture

Single binary, two modes:

1. CLI (rsdoc <command>): Thin client that forwards requests to the daemon.
2. Daemon (rsdoc daemon): Background process that does the heavy lifting — fetching docs, generating embeddings, running searches. Communicates over a Unix socket. Auto-spawned if not running, auto-exits after 10 minutes of inactivity.

Data lives in ~/.cache/ferrisfetch/:

• db.db — SQLite database with HNSW index
• cas/ — Content-addressable storage for documentation markdown
• json/ — Cached rustdoc JSON from docs.rs
• daemon.log — Daemon log output

License

See LICENSE.

Credits

• Voyage AI embeddings
• hann HNSW indexing
• docs.rs rustdoc JSON