cratesio-mcp

MCP server for querying crates.io -- the Rust package registry. Built with tower-mcp.

Gives your AI agent access to crate search, documentation, dependency analysis, download stats, and security auditing -- everything it needs to make informed decisions about Rust dependencies.

Quick start

Hosted (no install)

A public instance is running at https://cratesio-mcp.fly.dev/. Add to your MCP client config:

{
  "mcpServers": {
    "cratesio-mcp": {
      "type": "http",
      "url": "https://cratesio-mcp.fly.dev/"
    }
  }
}

Install from crates.io

cargo install cratesio-mcp

Build from source

git clone https://github.com/joshrotenberg/cratesio-mcp
cd cratesio-mcp
cargo install --path .

Docker

docker run -p 3000:3000 ghcr.io/joshrotenberg/cratesio-mcp:latest

MCP client configuration

Claude Code (stdio)

{
  "mcpServers": {
    "cratesio-mcp": {
      "command": "cratesio-mcp"
    }
  }
}

Claude Code (HTTP, local or remote)

{
  "mcpServers": {
    "cratesio-mcp": {
      "type": "http",
      "url": "http://localhost:3000/"
    }
  }
}

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "cratesio-mcp": {
      "command": "cratesio-mcp"
    }
  }
}

What's included

Tools (23)

Tool	Description
search_crates	Search for crates by name or keywords
get_crate_info	Detailed crate metadata (description, links, stats)
get_crate_versions	Version history with release dates and download counts
get_crate_version	Detailed metadata for a specific version
get_crate_readme	README content for a crate version
get_crate_features	Feature flags and their sub-feature activations
get_crate_docs	Browse documentation structure from docs.rs
get_doc_item	Full docs for a specific item (fn, struct, trait)
search_docs	Search for items by name within a crate's docs
get_dependencies	Dependencies for a specific version
get_reverse_dependencies	Crates that depend on a given crate
audit_dependencies	Check deps against OSV.dev vulnerability database
get_downloads	Download statistics and trends
get_version_downloads	Daily download stats for a specific version
get_crate_authors	Authors listed in Cargo.toml
get_owners	Crate owners and maintainers
get_user	User profile by GitHub username
get_user_stats	Total download stats for a user's crates
get_summary	crates.io global statistics
get_categories	Browse crates.io categories
get_category	Details for a specific category
get_keywords	Browse crates.io keywords
get_keyword	Details for a specific keyword

Resources (4)

Resource	Description
crates://{name}/info	Crate metadata
crates://{name}/readme	Crate README content
crates://{name}/docs	Documentation structure
Recent searches	Recent search queries and results

Prompts (2)

Prompt	Description
analyze_crate	Guided comprehensive crate analysis
compare_crates	Compare multiple crates side by side

Transports

• stdio (default) -- for Claude Desktop, Claude Code, and other MCP clients
• HTTP/SSE -- Streamable HTTP with server-sent events (MCP 2025-11-25 spec)

# stdio (default)
cratesio-mcp

# HTTP
cratesio-mcp --transport http --port 3000

The HTTP transport includes a tower middleware stack: timeout, rate limiting, bulkhead concurrency control, optional response caching, and structured tracing.

Library usage

The crate also exposes a typed async client for the crates.io API:

use std::time::Duration;
use cratesio_mcp::client::{CratesIoClient, CratesQuery, Sort};

let client = CratesIoClient::new("my-app", Duration::from_secs(1))?;

// Search for crates
let query = CratesQuery::builder()
    .search("tower")
    .sort(Sort::Downloads)
    .build();
let results = client.crates(query).await?;

// Get crate details
let info = client.get_crate("tower-mcp").await?;

The client covers 46 endpoints across crates, versions, owners, categories, keywords, users, teams, tokens, publishing, and trusted publishing.

License

MIT OR Apache-2.0