Rustdocs MCP Server

Rust is the language of AI

An MCP (Model Context Protocol) server that provides comprehensive access to
Rust crate documentation, source code analysis, dependency trees, and module
structure visualization. Built for agents to gain quality insights into Rust
projects and build with confidence.

Warning

This is an entirely vibe coded project and was created as an experiment to see if LLMs can build a fully functional tool without human oversight.

The Problem: Agents Building in the Dark

The rise of AI agents has revolutionized software development, with new tools
and libraries emerging at an unprecedented pace. However, this rapid evolution
creates a critical challenge: agents cannot reliably build with tools they
weren't trained on.

When an agent tries to use a new Rust crate:

🚫 Training data is outdated — The model hasn't seen recent crates or API
changes
🚫 Documentation scraping is inefficient — Web scraping GitHub or docs.rs
is slow and unreliable
🚫 Examples aren't enough — Copy-pasting README examples provides
surface-level understanding
🚫 Internal structure is opaque — Agents can't explore how modules,
traits, and types interconnect

This leads to frustrated developers watching their agents fail repeatedly,
guessing at APIs, and producing broken code.

The Solution: Deep Crate Intelligence

This MCP server gives agents the tools they need to truly understand Rust
crates:

🔍 Explore internal structure — Navigate module hierarchies and type
relationships
📖 Access complete documentation — Full rustdoc with signatures, fields,
and methods
🔗 Trace dependencies — Understand what a crate depends on and why
💾 Work offline — Cache crates locally for instant, reliable access
🎯 Query precisely — Search by pattern, kind, or path to find exactly
what's needed

With these capabilities, agents can build confidently with any Rust crate — even
ones released yesterday.

Agent Capabilities

Multi-source caching — crates.io, GitHub repositories, local
filesystem paths
Workspace support — Individual member analysis and caching for cargo
workspaces
Documentation search — Pattern matching with kind/path filtering and
preview modes
Item inspection — Detailed signatures, fields, methods, and
documentation strings
Source code access — Line-level precision with parameterized
surrounding context
Dependency analysis — Direct and transitive dependency trees with
metadata
Module structure — Hierarchical tree generation via cargo-modules
integration
Offline operation — Full functionality after initial crate caching
Token management — Response truncation and preview modes for LLM
compatibility

MCP Tools

Cache Management

cache_crate - Download and cache a crate from various sources. Set
source_type to one of: cratesio, github, or local
- For cratesio: Provide version (e.g., {crate_name: "serde", source_type: "cratesio", version: "1.0.215"})
- For github: Provide github_url and either branch OR tag (e.g., {crate_name: "my-crate", source_type: "github", github_url: "https://github.com/user/repo", tag: "v1.0.0"})
- For local: Provide path, optional version (e.g., {crate_name: "my-crate", source_type: "local", path: "~/projects/my-crate"})
remove_crate - Remove cached crate versions to free disk space
list_cached_crates - View all cached crates with versions and sizes
list_crate_versions - List cached versions for a specific crate
get_crates_metadata - Batch metadata queries for multiple crates

Documentation Queries

list_crate_items - Browse all items in a crate with optional filtering
search_items - Full search with complete documentation (may hit token
limits)
search_items_preview - Lightweight search returning only IDs, names, and
types
get_item_details - Detailed information about specific items (signatures,
fields, etc.)
get_item_docs - Extract just the documentation string for an item
get_item_source - View source code with configurable context lines

Dependency Analysis

get_dependencies - Analyze direct and transitive dependencies with filtering

Structure Analysis

structure - Generate hierarchical module tree using integrated cargo-modules

Search

search_items_fuzzy - Fuzzy search with typo tolerance and semantic
similarity

Configuration

Cache Directory

By default, crates are cached in ~/.rust-docs-mcp/cache/. You can customize
this location using:

# Command line option
rust-docs-mcp --cache-dir /custom/path/to/cache
# or set the environment variable
export RUST_DOCS_MCP_CACHE_DIR=/custom/path/to/cache
rust-docs-mcp

GitHub Authentication

To access private repositories or increase GitHub API rate limits, set the
GITHUB_TOKEN environment variable:

export GITHUB_TOKEN=your_github_personal_access_token

Benefits of authentication:

Access private repositories — Cache and analyze private Rust crates
Higher rate limits — 5,000 requests/hour (vs 60 unauthenticated)
Avoid rate limit errors — Essential for caching multiple GitHub-hosted
crates

Each crate version stores

Complete source code in source/ directory
Cache metadata and timestamps in metadata.json
For workspace crates, individual members in members/ directory:
- members/{member-name}/docs.json - Rustdoc JSON documentation
- members/{member-name}/dependencies.json - Cargo dependency metadata
- members/{member-name}/metadata.json - Member-specific cache metadata
For single crates:
- docs.json - Rustdoc JSON documentation
- dependencies.json - Cargo dependency metadata

Installation

Quick Install

curl -sSL https://raw.githubusercontent.com/snowmead/rust-docs-mcp/main/install.sh | bash

Installation Options

One-liner (Recommended)

curl -sSL https://raw.githubusercontent.com/snowmead/rust-docs-mcp/main/install.sh | bash

Custom install directory

curl -sSL https://raw.githubusercontent.com/snowmead/rust-docs-mcp/main/install.sh | bash -s -- --install-dir /usr/local/bin

Cargo Install

cargo install rust-docs-mcp

Building from Source

Requirements

Rust nightly toolchain (for Rustdoc JSON generation)
```
rustup toolchain install nightly
```
Network access to download crates from crates.io

git clone https://github.com/snowmead/rust-docs-mcp
cd rust-docs-mcp/rust-docs-mcp
cargo build --release
./target/release/rust-docs-mcp install

CLI Commands

rust-docs-mcp                   # Start MCP server
rust-docs-mcp install           # Install to ~/.local/bin
rust-docs-mcp install --force   # Force overwrite existing installation
rust-docs-mcp doctor            # Verify system environment and dependencies
rust-docs-mcp doctor --json     # Output diagnostic results in JSON format
rust-docs-mcp update            # Update to latest version from GitHub
rust-docs-mcp --help            # Show help

Troubleshooting

If you encounter issues during installation or runtime, run the doctor command
to diagnose common problems:

rust-docs-mcp doctor

The doctor command checks:

Rust toolchain availability (stable + nightly)
Git installation
Network connectivity to crates.io and GitHub
Cache directory permissions and disk space
Rustdoc JSON generation capability
Optional dependencies (e.g., codesign on macOS)

For programmatic integration, use --json flag to get structured output.

MCP Configuration

Add the server to your MCP configuration:

{
  "rust-docs": {
    "command": "/path/to/rust-docs-mcp/target/release/rust-docs-mcp",
    "transport": "stdio"
  }
}

rust-docs-mcp