Kastor is a tool that provides a vendor-neutral, versionable, and reviewable source of truth for AI agents. It offers a typed, declarative spec and a Go toolchain with two paths: kastor build and kastor plan/kastor apply. The tool requires Go 1.26+, Python 3.11+, an OpenAI API key, and a Tavily API key to function. Kastor allows users to compile specs to LangGraph projects and reconcile agents as long-lived resources on hosted platforms.