A developer has launched Skir, a new declarative language for defining data types, constants, and APIs that aims to improve upon Protocol Buffers. The tool generates idiomatic, type-safe code across TypeScript, Python, Java, C++, and more from a single YAML configuration file. The creator spent 15 years working with Protocol Buffers before building Skir.

Skir addresses several pain points in data serialization. The tool includes built-in safety checks for evolving schemas in long-lived or distributed systems, preventing breaking changes that could make old data unreadable. It also provides end-to-end type safety for RPCs, eliminating API contract mismatches between frontend and backend services or across microservices.

Additional features include serialization to JSON or binary formats, a built-in package manager for importing types directly from GitHub repositories, and a VS Code extension with real-time validation and code completion. The project is available on GitHub with documentation for getting started, and the creator is seeking feedback especially from teams running mixed-language stacks.