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crates.io

crates.io is the official package registry for the Rust programming language, operated by the crates.io team under the Rust Foundation with infrastructure support from Amazon Web Services and Fastly. It exposes a Web API at /api/v1 used by Cargo and the website for search, publishing, yanking, and owner management, plus a sparse HTTP index at index.crates.io that has been Cargo's default registry protocol since Rust 1.70 (June 2023). The legacy git index is still mirrored. Every published version is checksummed with SHA-256 and companion documentation is auto-built on docs.rs. The crates.io source code is dual-licensed under Apache-2.0 and MIT and runs on Rust (axum, diesel) with a SvelteKit frontend.

agent aware

Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.

Kin Score

API Evangelist profiles crates.io the way a machine reads it — 35 machine-readable artifacts across 5 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.

Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — crates.io scores 49.7/100 (developing), with a separate agent-readiness read of 41/100 (agent aware). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.

Kin Score

This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 49.7/100 · developing
Contract Quality 16.8 / 25
Developer Ergonomics 9.1 / 20
Commercial Clarity 0.0 / 20
Operational Transparency 6.2 / 13
Governance 8.8 / 12
Discoverability 8.8 / 10
Agent readiness — 41/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 15
MCP Server 0 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3

How we profile crates.io

Each block below is one kind of artifact we hold for crates.io. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.

APIs 5

Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.

Individual APIs this provider publishes, each with its own machine-readable definition.

crates.io Config API

Registry configuration document

crates.io Crates API

Search and manage Rust crates

crates.io Index API

Per-crate index metadata files served over HTTP

crates.io Owners API

List, add, and remove crate owners

crates.io Versions API

Yank and unyank crate versions

Open Collections 2

Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

crates.io Web API

OPEN COLLECTION

Features 14

The notable capabilities this provider advertises, captured as structured features so they can be searched and compared instead of read one landing page at a time.

Notable capabilities this provider offers.

Centralized package registry for the Rust programming language operated by the crates.io team under the Rust Foundation
Web API at https://crates.io/api/v1 for search, crate detail, version detail, download redirect, publish, yank, unyank, and owner management
Sparse HTTP index at https://index.crates.io (default for Cargo since Rust 1.70) — replaces the legacy git index for the vast majority of fetches
Legacy git index at https://github.com/rust-lang/crates.io-index still mirrored for source replacement and offline scenarios
SHA-256 checksums published per version for tamper-evident downloads
Index format v2 with features2 map for namespaced and weak-dep features
Per-crate keywords, categories, and reverse-dependency listings on the website
Authentication via per-user API tokens scoped to publish, yank, and owner-management permissions
Trusted Publishing flow via crates-io-auth-action exchanging GitHub Actions OIDC tokens for short-lived publish tokens
Open source under Apache-2.0 and MIT — backend in Rust (axum + diesel), frontend in SvelteKit/TypeScript
Infrastructure sponsored by Amazon Web Services (file hosting) and Fastly (CDN)
Status page at status.crates.io reporting crates.io and docs.rs uptime
Companion documentation host docs.rs auto-builds and serves docs for every published crate version
No paid plans — operated as a public good of the Rust ecosystem

Scroll within the panel for all 14 ·

Semantic Vocabularies 1

JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.

JSON-LD contexts and semantic vocabularies used across these APIs.

Crates Io Context

0 classes · 8 properties

JSON-LD

Spectral Rules 2

Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.

crates.io API Rules

6 rules · 5 warnings

SPECTRAL

crates.io API Rules

7 rules · 1 errors · 3 warnings

SPECTRAL

JSON Schema 2

Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.

Standalone JSON Schema definitions for this provider's data models.

crates.io Crate

4 properties

JSON SCHEMA

crates.io Sparse Index Entry

10 properties

JSON SCHEMA

JSON Structure 1

JSON Structure captures the data shapes in a form built for tooling — a complement to JSON Schema that keeps the model machine-legible.

JSON Structure definitions describing this provider's data shapes.

Crates Io Crate Structure

0 properties

JSON STRUCTURE

Examples 4

Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.

Example request and response payloads for these APIs.

Security Posture 3

Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Crates Io Authentication

apiKey · 1 scheme

SECURITY

Crates Io Domain Security

TLSv1.3 · DMARC

SECURITY

Crates Io Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.

Recommended x-agentic-access execution contracts for AI agents.

Crates Io Agentic Access

15 operations · 5 acting

15 operations · 5 acting

AGENTIC

Resources

Every other property we hold for crates.io — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.

Get Started 2

Portal, sign-up, and the first successful call

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

Commercial 2

Pricing, plans, and the legal terms of use

Company 1

The organization behind the API

Other 3

Properties that don't map to a standard resource type

← All providers · Data indexed from github.com/api-evangelist/crates-io · machine-readable index on apis.io