Smithy

Smithy is an open source, protocol-agnostic interface definition language (IDL) and toolchain developed at AWS for defining, validating, and generating API clients, servers, and documentation for any programming language. It powers the AWS SDK code generation pipeline and supports protocol-agnostic API modeling with traits, validators, and code generators. Smithy IDL 2.0 is the current stable version.

Smithy publishes 2 APIs on the APIs.io network. Tagged areas include Code Generation, IDL, SDK, API Design, and Interface Definition Language.

The Smithy catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.

Smithy’s developer surface includes documentation, getting-started guide, code examples, engineering blog, and 12 more developer resources.

🌐 Visit website 📡 Source on GitHub

27.4/100 thin ▬ flat Agent 4/100 human only self hosted · Apache-2.0 Full breakdown ↓
scored 2026-09-14 · rubric v0.22.0

AccessFreemium

2 APIs

Code Generation IDL SDK API DesignInterface Definition LanguageToolchain

Kin Score

Kin Score How this is scored →
scored 2026-09-14 · rubric v0.22.0

Composite quality — 27.4/100 · thin

Contract Quality 3.9 / 23

Developer Ergonomics 4.3 / 18

Access Clarity 2.8 / 18

Operational Transparency 3.1 / 12

Contract Governance 1.5 / 11

Discoverability 5.3 / 9

Open Source Surface 6.5 / 10

Agent readiness — 4/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Open Source Surface applies to this provider. This product is open source and we read its repository directly, so Open Source Surface carries 10 points of the composite. It is scored from what the repository actually publishes — a security policy, a contribution guide, a release history, a code of conduct — read live from the provider rather than inferred from our own catalog pointers. This facet adds; nothing was taken away to make room for it. An open-source project is not excused from the commercial facets, because exemption would strip it of the points it does earn. If we have the wrong repository, or this product is not open source, say so on your provider repo and we will drop the facet rather than have you publish against it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 90 points between them, because the conditional facet above carries the other 10. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 90% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/smithy: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 2

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

Smithy IDL

The Smithy Interface Definition Language (IDL) is a specification for defining API models using shapes and traits. Models can be written in the Smithy IDL syntax or the JSON AST...

Smithy CLI

The Smithy CLI is a command-line tool for building, validating, diffing, and transforming Smithy models. It can generate JSON AST representations, run model validation, perform ...

Pricing Plans 1

Published pricing tiers and plan structures.

Smithy Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Smithy Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Smithy Finops

FINOPS

Semantic Vocabularies 1

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

Smithy Context

26 classes · 0 properties

JSON-LD

Spectral Rules 2

Spectral governance rulesets for linting and validating these APIs.

Smithy API Rules

5 rules · 4 warnings 1 info

SPECTRAL

Smithy API Rules

5 rules · 1 errors 3 warnings 1 info

SPECTRAL

JSON Schema 2

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

Smithy Model (JSON AST)

3 properties

JSON SCHEMA

Smithy Shape

12 properties

JSON SCHEMA

JSON Structure 1

JSON Structure definitions describing this provider's data shapes.

Smithy Model Structure

0 properties

JSON STRUCTURE

Examples 1

Example request and response payloads for these APIs.

Smithy Simple Service Example

4 fields

EXAMPLE

Security Posture 1

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

Smithy Domain Security

TLSv1.3

SECURITY

Resources

Get Started 1

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

Documentation 3

Reference material describing how the API behaves

ContributionGuide

ContributionGuide

Documentation

Documentation

Specification

Specification

Build 4

SDKs, sample code, and the tooling you integrate with

CodeOfConduct

CodeOfConduct

GitHubOrganization

GitHubOrganization

GitHubRepository

GitHubRepository

Examples

Examples

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 2

Status, limits, changes, and where to get help

IssueTracker

IssueTracker

Releases

Releases

Commercial 1

Pricing, plans, and the legal terms of use

License

License

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 2

Properties that don't map to a standard resource type

Awesome List

Awesome List

AWS API Models

AWS API Models

Source (apis.yml)

aid: smithy
name: Smithy
description: Smithy is an open source, protocol-agnostic interface definition language (IDL) and toolchain developed at AWS
  for defining, validating, and generating API clients, servers, and documentation for any programming language. It powers
  the AWS SDK code generation pipeline and supports protocol-agnostic API modeling with traits, validators, and code generators.
  Smithy IDL 2.0 is the current stable version.
type: Index
deliveryModel:
  model: self-hosted
  license: Apache-2.0
  open_source: true
  commercial: false
  callable_host: false
  label: Self-hosted open source · you run it yourself
  confidence: high
  source:
  - license
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/smithy.png
tags:
- AWS
- Code Generation
- IDL
- SDK
- API Design
- Interface Definition Language
- Toolchain
tags_raw:
- AWS
- Code Generation
- IDL
- SDKs
- API Design
- Interface Definition Language
- Toolchain
created: '2026-03-25'
modified: '2026-05-02'
url: https://raw.githubusercontent.com/api-evangelist/smithy/refs/heads/main/apis.yml
specificationVersion: '0.23'
apis:
- aid: smithy:smithy-idl
  name: Smithy IDL
  description: The Smithy Interface Definition Language (IDL) is a specification for defining API models using shapes and
    traits. Models can be written in the Smithy IDL syntax or the JSON AST representation. Smithy 2.0 is the current stable
    version with improved nullability, enums, resource properties, and mixins.
  humanURL: https://smithy.io/2.0/
  tags:
  - IDL
  - API Design
  - Specification
  properties:
  - type: Documentation
    url: https://smithy.io/2.0/
  - type: Specification
    url: https://smithy.io/2.0/spec/
  - type: GettingStarted
    url: https://smithy.io/2.0/quickstart.html
  - type: GitHubRepository
    url: https://github.com/smithy-lang/smithy
- aid: smithy:smithy-cli
  name: Smithy CLI
  description: The Smithy CLI is a command-line tool for building, validating, diffing, and transforming Smithy models. It
    can generate JSON AST representations, run model validation, perform backwards-compatibility checks, and generate artifacts
    from Smithy models.
  humanURL: https://smithy.io/2.0/guides/smithy-cli/index.html
  tags:
  - CLI
  - Build Tools
  - Validation
  properties:
  - type: Documentation
    url: https://smithy.io/2.0/guides/smithy-cli/index.html
  - type: GitHubRepository
    url: https://github.com/smithy-lang/smithy
  - type: Homebrew
    url: https://github.com/smithy-lang/homebrew-tap
common:
- type: IssueTracker
  url: https://github.com/smithy-lang/smithy/issues
- type: Releases
  url: https://github.com/smithy-lang/smithy/releases
- type: CodeOfConduct
  url: https://github.com/smithy-lang/smithy/blob/main/CODE_OF_CONDUCT.md
- type: ContributionGuide
  url: https://github.com/smithy-lang/smithy/blob/main/CONTRIBUTING.md
- type: License
  name: Apache-2.0
  url: https://github.com/smithy-lang/smithy/blob/main/LICENSE
- type: DomainSecurity
  url: security/smithy-domain-security.yml
- type: Website
  url: https://smithy.io
- type: Documentation
  url: https://smithy.io/2.0/
- type: Specification
  url: https://smithy.io/2.0/spec/
- type: GettingStarted
  url: https://smithy.io/2.0/quickstart.html
- type: GitHubOrganization
  url: https://github.com/smithy-lang
- type: GitHubRepository
  url: https://github.com/smithy-lang/smithy
- type: Examples
  url: https://github.com/smithy-lang/smithy-examples
- type: Awesome List
  url: https://github.com/smithy-lang/awesome-smithy
- type: AWS API Models
  url: https://github.com/aws/api-models-aws
- type: Blog
  url: https://aws.amazon.com/blogs/developer/tag/smithy/
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

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