docsrs

Fast Rust documentation lookup for CLI and AI assistants.

Query docs.rs and local crate documentation with automatic version resolution, syntax-highlighted output, and MCP server integration for Claude.

Features

• Unified syntax: crate[@version][::path] - one format for all queries
• Smart version resolution: Automatically detects versions from your Cargo.toml
• Local crate support: Auto-builds documentation for workspace crates
• Syntax highlighting: Color-coded terminal output with markdown formatting
• MCP server: Integrates with Claude Code and other MCP-compatible AI tools
• Caching: Fast repeated queries with local documentation cache

Installation

From source

git clone https://github.com/human-solutions/mx-docsrs
cd mx-docsrs
cargo install --path crates/docsrs

Requirements

• Rust nightly toolchain (for local crate documentation):

  rustup toolchain install nightly

Usage

Basic queries

# View crate root documentation
docsrs tokio

# Navigate to specific item
docsrs tokio::spawn
docsrs serde::Deserialize

# Deep path navigation
docsrs tokio::sync::mpsc::channel

Version specification

# Explicit version
docsrs tokio@1.35.0

# Version requirement
docsrs serde@^1.0

# From your Cargo.toml (automatic)
docsrs tokio  # uses version from your project's dependencies

Filtering

# Search within a crate
docsrs tokio spawn         # items containing "spawn"

# Search within a module
docsrs tokio::sync mutex   # items in tokio::sync containing "mutex"

Options

# Clear documentation cache
docsrs --clear-cache

# Skip cache for fresh fetch
docsrs --no-cache tokio

# Control color output
docsrs --color=always tokio
docsrs --color=never tokio

MCP Server

docsrs includes an MCP (Model Context Protocol) server for integration with Claude Code and other AI assistants.

Setup with Claude Code

Add to your Claude Code MCP configuration:

{
  "mcpServers": {
    "docsrs": {
      "type": "stdio",
      "command": "docsrs",
      "args": ["--mcp"]
    }
  }
}

Tool

The MCP server exposes a single tool:

lookup_docs

• crate_spec (required): Crate path like tokio, serde@1.0, or tokio::spawn
• filter (optional): Search term to filter results

How It Works

Version Resolution

When you query a crate without an explicit version:

1. Direct dependency: Uses the version from your Cargo.toml
2. Transitive dependency: Resolves through the dependency chain
3. Local/workspace crate: Builds documentation with cargo +nightly doc
4. Not found: Falls back to latest version on docs.rs

Documentation Sources

• Published crates: Fetches pre-built JSON from docs.rs
• Local crates: Builds documentation using cargo +nightly doc with JSON output
• Cached: Stores downloaded documentation for fast subsequent queries

Error Handling

• Missing nightly: Clear error message with installation instructions
• Build failures: Uses cached documentation with a warning if available

Project Structure

Crate	Description
docsrs	Main binary (CLI and MCP server)
docsrs-core	Core CLI logic and documentation fetching
docsrs-mcp	MCP server implementation
jsondoc	Rustdoc JSON processing
rustdoc-fmt	Terminal markdown formatting with syntax highlighting

License

MIT OR Apache-2.0