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Smithy

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What Smithy is

Smithy is an open-source interface definition language and toolset for teams modeling service APIs and generating implementation artifacts. A shared model can produce type-safe client SDKs in ten languages, server code, API reference documentation, OpenAPI, and JSON Schema. The same service model can describe REST JSON, RPC v2 CBOR, AWS JSON, and AWS Query/XML protocols. Resource-based modeling can also generate artifacts such as CloudFormation schemas. During a smithy build, the tool validates model standards and checks revisions for backward compatibility. The Smithy CLI can build, validate, compare, and query models without requiring Java or Smithy Gradle Plugins. It is supported on macOS x86 and ARM, Linux x86 and ARM, and Windows x64. Build configurations can load extensions and code generators through Maven dependencies and plugins, including AWS-specific dependencies and an OpenAPI generator. The project says Smithy was created and is used at AWS, where it powers APIs and SDKs. Smithy is maintained by AWS and the open-source community under the Apache 2.0 license; the site directs users to GitHub issues for suggestions and problems.

Who it suits

Smithy suits teams defining service APIs that need to generate SDKs, server code, or documentation across programming languages. It is also relevant to teams working with the listed REST and AWS protocols or OpenAPI.

What it does well

  • Generates clients in ten languages.
  • Supports server code in five languages.
  • Checks model revisions for backward compatibility.
  • CLI runs on macOS, Linux, and Windows.
  • Open source under Apache 2.0.

What to know first

  • CLI support on Windows is limited to x64.
  • CLI requires platform-specific architecture support.

Limits

Server support is listed for TypeScript, Java, Python, Go, and Rust. The Smithy CLI supports macOS x86 and ARM, Linux x86 and ARM, and Windows x64.

Getting started

  1. Open the Smithy website
  2. Download the Smithy CLI for macOS, Linux, or Windows
  3. Verify the archive signature and checksum
  4. Use the CLI to build, validate, compare, or query models
  5. Configure Maven dependencies or plugins for extensions and code generators as needed

Verdict

Smithy provides a shared API model with validation and generation for clients, servers, and documentation. Its protocol and language coverage makes it suited to teams that want these outputs from one model.

Questions

Is Smithy free?

Yes. Smithy is free and open source under the Apache 2.0 license.

Which client languages can Smithy generate?

The listed client SDK languages are TypeScript, Python, Go, Rust, Kotlin, Swift, Java, Scala, Ruby, and Dafny.

Which server languages are supported?

Smithy lists server support for TypeScript, Java, Python, Go, and Rust.

Does Smithy support OpenAPI?

Yes. A model can generate OpenAPI, and build configurations can load an OpenAPI generator.

What operating systems support the CLI?

The CLI supports macOS x86 and ARM, Linux x86 and ARM, and Windows x64.

How does Smithy relate to AWS?

Smithy says it was created and is used at AWS, where it powers AWS APIs and SDKs. It documents integrations with API Gateway, CloudFormation, and AWS SDKs.

Facts from Smithy's own pages

API protocols
The same service model can support REST JSON, RPC v2 CBOR, AWS JSON, and AWS Query/XML protocols. · smithy.io, 4 Oct 2026
AWS integrations
Smithy documents integrations with AWS services and tools including API Gateway, CloudFormation, and AWS SDKs. · smithy.io, 9 Oct 2026
AWS use
Smithy says it was created and is used at AWS, and that it powers AWS APIs and SDKs. · smithy.io, 4 Oct 2026
CLI
The Smithy CLI can build models, run ad hoc validation, compare models, and query models without requiring users to set up Java or Smithy Gradle Plugins. · smithy.io, 4 Oct 2026
Client languages
The site lists client SDKs for TypeScript, Python, Go, Rust, Kotlin, Swift, Java, Scala, Ruby, and Dafny. · smithy.io, 9 Oct 2026
CLI platforms
The Smithy CLI is supported on macOS for x86 and ARM, Linux for x86 and ARM, and Windows x64. · smithy.io, 9 Oct 2026
Code generation
A single Smithy model can generate type-safe clients, servers, documentation, OpenAPI, and JSON Schema. · smithy.io, 9 Oct 2026
Community and maintenance
The site says Smithy is maintained by AWS and the open-source community and links to community resources and GitHub issues. · smithy.io, 9 Oct 2026
Download verification
Smithy CLI release archives are PGP-signed and hashed, and the installation guide describes verifying their signatures and checksums. · smithy.io, 4 Oct 2026
Governance
Smithy validates model standards during smithy build and checks revisions for backward compatibility. · smithy.io, 9 Oct 2026
Integrations
Smithy build configurations can load extensions and code generators through Maven dependencies and plugins, including AWS-specific dependencies and an OpenAPI generator. · smithy.io, 4 Oct 2026
Intended users
Smithy is presented for teams defining service APIs and generating SDKs, server code, and documentation across programming languages. · smithy.io, 4 Oct 2026
License
The site identifies Smithy as open source under the Apache 2.0 license. · smithy.io, 9 Oct 2026
Modeling
Smithy supports resource-based API modeling, which can be used to generate artifacts including CloudFormation schemas, SDKs, and documentation. · smithy.io, 4 Oct 2026
Product
Smithy is an open-source, protocol-agnostic interface definition language and toolset for defining APIs and generating clients, servers, and documentation. · smithy.io, 4 Oct 2026
Protocols
Smithy describes support for REST JSON, RPC v2 CBOR, AWS JSON, and AWS Query protocols. · smithy.io, 9 Oct 2026
Purpose
Smithy is an open-source interface definition language for modeling services and SDKs. · smithy.io, 9 Oct 2026
Security
The Smithy CLI installation guide says release archives are PGP-signed and hashed, and describes verifying signatures and checksums. · smithy.io, 9 Oct 2026
Server languages
The site lists server support for TypeScript, Java, Python, Go, and Rust. · smithy.io, 9 Oct 2026
Support
The CLI guide directs users with suggestions or issues to create an issue in the Smithy GitHub repository. · smithy.io, 4 Oct 2026
Supported CLI platforms
The Smithy CLI is supported on macOS x86 and ARM, Linux x86 and ARM, and Windows x64. · smithy.io, 4 Oct 2026

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