Ferritin — Rust documentation

rs.ferritinPublished by ferritin.rsOfficial publisherv2026.7.21Updated Oct 24, 2026

Search and read Rust documentation for the standard library and any crate on crates.io

VerifiedStreamable HTTPWeb executableKnowledge & MemoryDeveloper Tools

Overview

AI-generated overview

A remote MCP server that lets an assistant look up and search Rust documentation for the standard library and crates.io crates.

What you can do
Look up documentation for a Rust item by its path, such as a standard library type or a crate's trait, and get its rendered docs and signature details back in the conversation. Search within a specific crate's documentation for items matching a query, or search without naming a crate to discover which crate provides what you need. Together these cover the common loop of finding the right crate, then reading the exact item's documentation without leaving the assistant.
When to use it
Useful when writing or debugging Rust code and you want the assistant to check real API documentation for std or a crates.io crate instead of relying on memory. Also handy for choosing between crates or locating an item whose exact path you do not know.
Requirements
A remote MCP endpoint; no local install, account, API key or environment variables are declared. The assistant needs network access to the endpoint, and the server fetches crate documentation from docs.rs on demand.
Before you install
The server is read-only documentation lookup, but queries and requested item paths are sent to a third-party endpoint, and crate documentation is fetched from docs.rs, so your lookups are visible to those services. Documentation reflects published crate versions and may lag behind the latest release.

Installation

In SourceWeft

  1. Open Ferritin — Rust documentation in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/rs.ferritin%2Frustdoc/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "ferritin-rust-documentation": {
      "type": "http",
      "url": "https://ferritin.rs/mcp"
    }
  }
}

README

🩸 Ferritin

[ci] [codecov] [crates.io version badge]

A terminal-based Rust documentation viewer

Ferritin reads rustdoc JSON output to display Rust documentation directly in your terminal. It supports local workspace crates, standard library documentation, and crates from crates.io, with search functionality and modern terminal features including mouse support, syntax highlighting, and clickable links.

Features

  • Interactive documentation browser with keyboard and mouse navigation
  • One-shot CLI for quick documentation lookups in the terminal
  • Search across crates or within specific crates
  • Works seamlessly across three contexts:
    • Local workspace crates (requires nightly toolchain)
    • Standard library (requires rust-docs-json rustup component)
    • Crates from crates.io (fetched from docs.rs on demand)
  • Modern terminal UI with features like italics, unicode box drawing, syntax highlighting, OSC8 hyperlinks, cursor changes in terminals that support it, and mouse hover previews
  • Fast navigation with history and breadcrumb trail

Installation

Prebuilt binary (recommended)

Prebuilt binaries skip compilation and are available for x86_64/aarch64 macOS, x86_64 Linux, and x86_64 Windows.

If you have cargo-binstall, it reads the release metadata and installs the right binary for your platform:

bash
cargo binstall ferritin

Otherwise, the installer scripts detect your platform, download the matching binary, and place it in ~/.cargo/bin:

macOS and Linux:

bash
curl --proto '=https' --tlsv1.2 -LsSf https://github.com/jbr/ferritin/releases/download/ferritin-latest/ferritin-installer.sh | sh

Windows (PowerShell):

powershell
powershell -c "irm https://github.com/jbr/ferritin/releases/download/ferritin-latest/ferritin-installer.ps1 | iex"

Both of the above always install the most recent release. You can also pick a specific version or download archives directly from the releases page.

From source

To build from source (or for a platform without a prebuilt binary):

bash
cargo install ferritin

Optional: Standard library documentation

To view documentation for std, core, and alloc:

bash
rustup component add rust-docs-json

For local workspace documentation

Local crate documentation requires a nightly toolchain:

bash
rustup toolchain install nightly

Note: There is a relationship between ferritin's version and the nightly toolchain version. Ferritin supports a range of recent rustdoc JSON format versions, and if your nightly generates a newer format, ferritin will make a best effort at parsing it.

Usage

Interactive mode

Launch the interactive browser:

bash
ferritin -i

Once running, use h or ? to see available keybindings. Basic navigation:

  • g - go to an item by path (e.g., std::vec::Vec)
  • s - search (Tab to toggle between current crate and all crates)
  • l - list available crates
  • Arrow keys, j/k, or mouse to navigate
  • Click on links to follow them

CLI mode

View documentation for a specific item:

bash
ferritin get std::vec::Vecferritin get serde::Serialize

Search for items:

bash
ferritin search "hash map"ferritin search --crate tokio "spawn"

List available crates in your workspace:

bash
ferritin list

Output format

Ferritin auto-detects how to render: ANSI colors on a terminal, plain text when piped, and a compact markdown-flavored format under a coding agent. Override it with --format <tty|plain|agent|json>. --format json emits a structured representation — of the resolved item for get, or of the results for search/list — for scripting and programmatic consumers:

bash
ferritin get std::vec::Vec --format json

(The JSON shape is still settling as the library API evolves; a published JSON Schema is planned.)

Caching and Storage

Ferritin keeps its caches under a single directory — $FERRITIN_HOME if set, else $XDG_CACHE_HOME/ferritin, else ~/.cache/ferritin. Everything in it is reconstructible (fetched or derived), so it is always safe to delete:

  • Crates.io documentation: raw rustdoc JSON at docs/{crate}/{version}/{format-version}.json, with derived binary caches beside it (an rkyv archive for fast partial loads, and a .index file generated lazily on first search)
  • crates.io metadata: the crate-names artifacts (crate-names/) used for version resolution and typeahead, and per-crate version lookups (crates-io-versions/)
  • Standard library search indices: written to {rustc sysroot}/share/doc/rust/json/ if available
  • Local workspace documentation: built into the workspace's own target/doc/, not the shared cache

Earlier versions cached under $CARGO_HOME/rustdoc-json; a cache found there is migrated automatically on first run.

Environment Variables

VariableMeaning
FERRITIN_HOMECache root override (see above)
FERRITIN_THEMEDefault color theme (equivalent to --theme)
FERRITIN_CRATE_NAMES_URL, FERRITIN_CRATE_DESCRIPTIONS_URLOverride where the crate-names artifacts are fetched from (e.g. a mirror)

ferritin serve (the opt-in serve/acme features; not present in distributed binaries) is configured 12-factor style:

VariableMeaning
HOST, PORTBind address (:: binds dual-stack)
FERRITIN_CACHE_BYTESIn-memory crate-cache weight cap
FERRITIN_RSS_HIGH_WATER_BYTESRSS guard threshold (Linux only): shed cache weight when anonymous RSS exceeds it
FERRITIN_RATELIMITPer-client /api requests per minute
FERRITIN_ACME_DOMAINActivates automatic HTTPS via Let's Encrypt for this domain
FERRITIN_ACME_CACHE_DIRRequired with ACME: persists the account key and certificates
FERRITIN_ACME_CONTACTOptional ACME contact email
FERRITIN_ACME_PRODUCTIONUse the Let's Encrypt production directory (default: staging)

Development-only knobs (not part of the stable interface): FERRITIN_TEST_MODE (normalized snapshot-test output), FERRITIN_REINDEX (rebuild search indexes in memory, bypassing the disk cache), and the search-scoring probes FERRITIN_NAME_WEIGHT, FERRITIN_ANCESTOR_WEIGHTS, and FERRITIN_NAME_PREFIX_COUNT.

Current Status

Ferritin is at version 0.x and actively used by the author as a primary documentation interface. It's ready for general use, though the output format should be considered unstable and may change between versions.

If you're scripting against ferritin's output, be aware that the text format may change. Pin to a specific version or be prepared to update your scripts.

Platform Support

Ferritin is developed primarily on Unix-like systems and is also tested on Windows, where both the CLI and interactive TUI work (prebuilt x86_64 Windows binaries are provided). If you encounter issues on any platform, please open an issue or pull request.

Related Projects

Ferritin was originally developed to support the rustdoc-mcp MCP server, which provides Rust documentation access for Claude Code and other MCP clients.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Source: README.md at commit 3770aa6

Tools

2

get

Show documentation for a Rust item by path.

Parameterspathrequired

Version history

1
  1. v2026.7.21LatestSep 16, 2026

Score

100% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts