Smithy
Smithy: A model-first toolkit for defining, validating, transforming, and generating APIs. Ranked #8 of 27 in API Design Tools by our editors (8.1/10); pricing: Open source; best for teams using model-first, protocol-agnostic API design.
At a glance
- Editor score8.1 / 10
- PricingOpen source
- Best forTeams using model-first, protocol-agnostic API design
- Paid fromFree
- Team collaborationYes
- Facts checked20 Sep 2026
Where it wins
- Defines services and APIs independently of wire protocol
- Generates client, server, and reference documentation outputs
- Converts models to OpenAPI and supports AWS integrations
Where it doesn't
- Local CLI rather than a hosted API design SaaS product
- Requires model-driven workflows and build plugins
- Paid plans and hosted collaboration details are not provided
Our verdict on Smithy
Smithy is an open-source interface definition language and build tool for designing services and APIs. It is aimed at teams that want to define a service model once and use that model across validation, code generation, documentation, and specification conversion. Its model-first approach covers resource- and operation-based definitions, custom traits, multiple wire protocols, and event-stream definitions. Smithy runs on Windows, macOS, and Linux, making it suitable for development environments that support a local CLI workflow.
The main strength is breadth across the API lifecycle. Configurable linters and model validation help check definitions, while Smithy Build plugins can generate client and server code, API reference documentation, OpenAPI specifications, and JSON Schema. Model projections and transformations add another layer for adapting service models to different outputs. The published capabilities also include language targets such as TypeScript, Python, Go, Rust, Java, Kotlin, Swift, Scala, Ruby, and Dafny, giving teams several implementation paths without changing the core modeling approach.
Smithy fits especially well where protocol neutrality, generated artifacts, and AWS ecosystem connections matter. Integrations include Amazon API Gateway, AWS CloudFormation, and AWS IAM. It is also open source, but its product shape differs from hosted API design platforms: Smithy is presented as a local CLI and modeling tool, not a managed workspace. Teams seeking a model-first foundation with OpenAPI conversion and code generation should consider it; teams prioritizing a hosted collaboration experience or packaged paid tiers should choose a product built around those capabilities instead.
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Smithy pricing
Smithy fact sheet
| Free plan | Not verified |
|---|---|
| Paid from | Free |
| OpenAPI support | Yes |
| AsyncAPI support | Not verified |
| Mock server | Not verified |
| Contract validation | Not verified |
| Git synchronization | Not verified |
| Team collaboration | Yes |
| Included team seats | Not verified |
| Deployment | Self-hosted |
| Platforms | Windows, macOS, Linux |
| Support | Community, Docs |
| Built for | Small business, Mid-market, Enterprise (editorial estimate) |
| Integrations | 3 integrations: Amazon API Gateway, AWS CloudFormation, AWS IAM See all → |
| Pricing | Open source |
| Website | smithy.io |
| Facts checked | 20 Sep 2026 |
Smithy integrations
Smithy lists 3 integrations on its own site.
- Amazon API Gateway
- AWS CloudFormation
- AWS IAM
Alternatives to Smithy
- ApidogAn all-in-one API suite spanning design, testing, mocks, documentation, and CI/CD.9.4
- PostmanA broad API workspace spanning design, testing, mocks, documentation, and CI/CD.9.2
- OpenAPI StudioA collaborative OpenAPI workspace with visual design, execution, validation, and GitHub sync.9.1
Smithy vs the competition
- Smithy vs Apidog
- Smithy vs Postman
- Smithy vs OpenAPI Studio
- Smithy vs SwaggerHub
- Smithy vs WSO2 API Designer
- Smithy vs Swagger Editor
Compare Smithy with any tool side by side →
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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