OpenAPI Generator vs Stainless

OpenAPI Generator produces API clients, server stubs, and documentation from OpenAPI 2.0 and 3.x documents. It offers more than 50 client generators and server stub generation for over 40 languages and technologies, including Java, Kotlin, Go, and PHP. Other outputs include Apache2 configuration, MySQL, GraphQL schemas, and formats such as HTML and Cwiki. It can also convert OpenAPI 2.0 documents into OpenAPI 3.x JSON or YAML. Generated output can be adapted with Mustache templates, configuration-provided files and extensions, or custom generators. Installation choices include npm, Homebrew, Scoop, PyPI, Docker, JAR, JBang, and a Bash launcher. The project documents Gradle, Maven, sbt, Bazel, GitHub, and CI/CD integrations. Supported operating systems include Linux, macOS, and Windows, though installer availability varies by system. The JAR option requires Java 11 or later. The project is free and describes a Slack community for questions and guidance.

Stainless generates SDKs, documentation and MCP servers from OpenAPI specifications. Its SDK product lists TypeScript, Python, Go, Java, Kotlin, Ruby, Terraform, C# and PHP, with rich types, automatic pagination and retries included. The Docs Platform, built on Astro, keeps REST API, SDK and narrative documentation in sync with an API. Its listed features include AI-powered hybrid search, Markdown copying, AI-tool integration, and light and dark modes. Stainless also generates code-mode MCP servers so agents can work with SDKs and documentation rather than many endpoint schemas; the MCP product page names Claude Code and Cursor as clients. The Free plan costs nothing and allows up to five generators, five seats and 25 endpoints, with 100 preview builds per month and a rate limit of 25 per day. Email support is listed for Free. Users need a GitHub account for authentication and access to generated staging repositories. Exceeding Free plan terms triggers automatic enrollment in a 30-day free trial of a paid plan. Code generation cannot be hosted on-premise, although generated SDKs can be hosted in a private GitHub repository.