# cratesio-mcp
[](https://crates.io/crates/cratesio-mcp)
[](https://docs.rs/cratesio-mcp)
[](https://github.com/joshrotenberg/cratesio-mcp/actions/workflows/ci.yml)
[](https://github.com/joshrotenberg/cratesio-mcp#license)
[](https://github.com/joshrotenberg/cratesio-mcp)
[MCP](https://modelcontextprotocol.io) server for querying [crates.io](https://crates.io) -- the Rust package registry. Built with [tower-mcp](https://github.com/joshrotenberg/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.
Under the hood it's also a standalone, dependency-light **crates.io API client library** -- ~46 endpoints with full read *and* write coverage, no `crates_io_api` dependency -- that the MCP tools are built on and that you can use directly. See [Built-in crates.io client](#built-in-cratesio-client).
## Quick start
### Hosted (no install)
A public instance is running at **https://cratesio-mcp.fly.dev/**. Add to your MCP client config:
```json
{
"mcpServers": {
"cratesio-mcp": {
"type": "http",
"url": "https://cratesio-mcp.fly.dev/"
}
}
}
```
### Install from crates.io
```bash
cargo install cratesio-mcp
```
### Build from source
```bash
git clone https://github.com/joshrotenberg/cratesio-mcp
cd cratesio-mcp
cargo install --path .
```
### Docker
```bash
docker run -p 3000:3000 ghcr.io/joshrotenberg/cratesio-mcp:latest
```
## MCP client configuration
### Claude Code (stdio)
```json
{
"mcpServers": {
"cratesio-mcp": {
"command": "cratesio-mcp"
}
}
}
```
### Claude Code (HTTP, local or remote)
```json
{
"mcpServers": {
"cratesio-mcp": {
"type": "http",
"url": "http://localhost:3000/"
}
}
}
```
### Claude Desktop
Add to `claude_desktop_config.json`:
```json
{
"mcpServers": {
"cratesio-mcp": {
"command": "cratesio-mcp"
}
}
}
```
## What's included
### Tools (29)
| `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 |
| `compare_crates` | Compare two or more crates side by side (downloads, versions, dependencies, freshness) |
| `get_dependency_tree` | Full transitive dependency tree with configurable depth and deduplication markers |
| `get_crate_health` | Comprehensive health report (maturity, adoption, maintenance, security, dependency weight) |
| `get_alternatives` | Find and compare alternative crates based on keywords, downloads, and recent activity |
| `get_crate_changelog` | Changelog content from a crate's GitHub repository, optionally filtered to a version |
| `get_release_timeline` | Version-over-version registry-metadata diff: feature changes, MSRV bumps, yanked status, release cadence |
### Resources (4)
| `crates://{name}/info` | Crate metadata |
| `crates://{name}/readme` | Crate README content |
| `crates://{name}/docs` | Documentation structure |
| Recent searches | Recent search queries and results |
### Prompts (6)
| `analyze_crate` | Guided comprehensive crate analysis |
| `compare_crates_analysis` | Compare multiple crates side by side |
| `stack_review` | Evaluate a set of crates as a cohesive stack for compatibility and health |
| `evaluate_dependencies` | Evaluate a project's dependencies for health, security, and maintenance |
| `recommend_crates` | Find and evaluate crates for a given use case |
| `migration_guide` | Generate a migration guide for switching between two crates |
## 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)
```bash
# stdio (default)
cratesio-mcp
# HTTP
cratesio-mcp --transport http --port 3000
```
The HTTP transport includes a [tower](https://github.com/tower-rs/tower) middleware stack: timeout, rate limiting, bulkhead concurrency control, optional response caching, and structured tracing.
## Built-in crates.io client
`cratesio-mcp` is built on its own typed async crates.io API client -- **no `crates_io_api` dependency**. It's a first-class part of the crate, not an afterthought, and you can use it directly as a library:
- **~46 endpoints** across crates, versions, owners, categories, keywords, users, teams, API tokens, publishing, and trusted publishing.
- **Full read *and* write coverage** -- search and metadata, plus authenticated operations (publish, yank/unyank, add/remove owners, manage API tokens, configure trusted publishing) via `.with_auth(token)`.
- **Resilient by default** -- built-in rate limiting (respects the crates.io crawling policy) and retry with exponential backoff on transient failures (429 / 5xx).
- **Documented and tested** -- every public method has doc comments, with a wiremock test suite covering the endpoints (including the authenticated write paths).
```rust
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 OSV.dev vulnerability client (`audit_dependencies`) and the docs.rs rustdoc-JSON client (`get_crate_docs` / `get_doc_item` / `search_docs`) ship alongside it.
## License
MIT OR Apache-2.0