Search and read Rust documentation for the standard library and any crate on crates.io
rs.ferritin/rustdoc MCP Server
The rs.ferritin/rustdoc server provides terminal-based Rust documentation search and viewing. It “reads rustdoc JSON output to display Rust documentation” for the Rust standard library and crates on crates.io. It exposes two tools for these documentation lookup and reading workflows.
🛠️ Key Features
Search and read Rust documentation for the standard library and crates on crates.io
Displays documentation in a terminal using rustdoc JSON output
Tool count: 2
🚀 Use Cases
Look up Rust standard library documentation from rustdoc JSON
Browse documentation for crates published on crates.io
Read Rust docs directly in a terminal environment
⚡ Developer Benefits
Integrates Rust documentation viewing via rustdoc JSON
Avoids leaving the terminal when searching and reading docs
⚠️ Limitations
Documentation viewing is based on rustdoc JSON output
Captured live from the server via tools/list.
get
Show documentation for a Rust item by path.
Parameters1
path
string
required
Item path, e.g. `serde::Deserialize` or `std::vec::Vec`. A crate segment
may carry an `@`-suffixed semver requirement (not an exact version):
`tokio@1::runtime::Runtime` serves the newest 1.x, while `tokio@=1.40`
pins an exact release.
Raw schema
{
"type": "object",
"properties": {
"path": {
"description": "Item path, e.g. `serde::Deserialize` or `std::vec::Vec`. A crate segment\nmay carry an `@`-suffixed semver requirement (not an exact version):\n`tokio@1::runtime::Runtime` serves the newest 1.x, while `tokio@=1.40`\npins an exact release.",
"type": "string"
}
},
"required": [
"path"
],
"examples": [
{
"description": "Look up a trait",
"path": "serde::Deserialize"
}
]
}
search
Search for items within a single crate by name or documentation.
Parameters2
crate
string
required
Crate to search, optionally with an `@`-suffixed semver requirement (not
an exact version): `serde`, `tokio@1` (newest 1.x), or `tokio@=1.40` to
pin an exact release.
query
string
required
Search query — one or more words matched against item names and prose.
Raw schema
{
"type": "object",
"properties": {
"crate": {
"description": "Crate to search, optionally with an `@`-suffixed semver requirement (not\nan exact version): `serde`, `tokio@1` (newest 1.x), or `tokio@=1.40` to\npin an exact release.",
"type": "string"
},
"query": {
"description": "Search query — one or more words matched against item names and prose.",
"type": "string"
}
},
"required": [
"crate",
"query"
],
"examples": [
{
"crate": "serde",
"description": "Find deserialization items in serde",
"query": "deserialize"
}
]
}
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
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::Vec
ferritin 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.
Override 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:
Variable
Meaning
HOST, PORT
Bind address (:: binds dual-stack)
FERRITIN_CACHE_BYTES
In-memory crate-cache weight cap
FERRITIN_RSS_HIGH_WATER_BYTES
RSS guard threshold (Linux only): shed cache weight when anonymous RSS exceeds it
FERRITIN_RATELIMIT
Per-client /api requests per minute
FERRITIN_ACME_DOMAIN
Activates automatic HTTPS via Let's Encrypt for this domain
FERRITIN_ACME_CACHE_DIR
Required with ACME: persists the account key and certificates
FERRITIN_ACME_CONTACT
Optional ACME contact email
FERRITIN_ACME_PRODUCTION
Use 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.
Install
Tools (2)
getsearch
Remote endpoint
Streamable HTTP
Hosted server - connect over the network, no local install.
