January 2026 Summaries

Stainless has introduced a feature that allows developers to generate command line tools directly from their OpenAPI specifications, streamlining the creation of high-quality CLI interfaces. These tools, which are built as wrappers around Go SDKs due to Go's performance and distribution advantages, provide scriptable and efficient ways for developers to interact with APIs. Stainless's solution simplifies the traditionally complex process of building CLIs by handling aspects like argument parsing, pagination, shell completions, and cross-platform distribution, ensuring ease of use for end users across macOS, Linux, and Windows. The CLI tools are designed with a resource-based structure and support intuitive syntax for common use cases, as well as advanced input methods for complex data. Additionally, the CLIs are self-documenting, making them suitable for both human users and AI agents by offering clear documentation and predictable command structures. Through integration with the existing release flow, Stainless ensures that CLI tools are distributed seamlessly alongside other SDKs, with support for package managers like Homebrew and plans for further expansions to npm.

PHP continues to be a crucial component of the internet, powering a significant number of websites and frameworks like Laravel and Wordpress. Recognizing the importance of PHP developers, the announcement of the PHP SDK generator's general availability aims to support API adoption by offering tools that align with PHP conventions while allowing for complex use cases. The generator emphasizes consistency with existing language practices, utilizing value objects as foundational elements, which facilitate ease of use and integration. These value objects simplify interactions by supporting both PHP arrays and structured data, making them adaptable for various use cases, such as paginated endpoints and custom request options. The design prioritizes seamless integration into existing PHP practices, ensuring minimal disruption while enhancing functionality. Real-world usage by companies like Anthropic, Browserbase, and Courier underscores the SDK's effectiveness, providing robust typing without sacrificing flexibility. The generator's design achieves a balance of modern typing and predictable behavior, positioning it as a valuable tool for developers looking to build scalable and efficient PHP applications.

C# plays a versatile role in the programming ecosystem, powering enterprise software, AAA games, and front-end web development through frameworks like Blazor. Stainless aims to create idiomatic SDKs for C# that align with the language's strengths, offering features such as strong typing, LINQ composition, and robust tooling support. The recent GA release of their C# SDK generator, which has evolved since its beta launch, supports .NET Standard 2.0, enabling compatibility across various .NET environments. The generator's design decisions emphasize idiomatic code and advanced functionality, even in the absence of native support for certain features. To accommodate the splintered .NET ecosystem, the SDKs are crafted for wide compatibility, featuring immutable record classes and type-safe models that facilitate flexibility in adhering to or deviating from OpenAPI specs. The SDKs also manage unions effectively without sacrificing type safety, and they include built-in testing and minimal dependencies, making them suitable for long-term maintainability. Trusted by production teams at companies like Anthropic and Arcade AI, these SDKs are designed to seamlessly integrate into .NET codebases, supporting developers in building reliable software.

Engineering leaders at API companies frequently sought advice from Alex, the creator of the SDK generator used at Stripe, regarding the necessity of language-specific SDKs for REST APIs. Alex's experience suggests that such SDKs are beneficial as they enhance API adoption, reduce implementation time, lower support burdens, and are often seen as a mark of maturity by enterprises. Despite their advantages, historically, creating and maintaining SDKs was complex and costly, requiring significant resources and expertise. However, tools like the Stainless SDK generator, modeled after Stripe's technology, now facilitate the production of high-quality SDKs, making them accessible to more companies. Language-specific SDKs are particularly vital in enabling AI agents to effectively integrate with APIs by providing strongly-typed interfaces that can be statically analyzed for correctness. While not all APIs may require SDKs, especially simpler ones with stable data structures, for most APIs, having robust language-specific SDKs can unblock potential customers and provide a competitive edge.