Semantic Kernel is Microsoft's answer to LangChain, built from the start with enterprise .NET and Java shops in mind rather than Python-first the way most of the agent framework ecosystem has been. It provides the usual building blocks, prompt templates, memory, planning, and tool calling, wrapped in an SDK that fits naturally into existing enterprise codebases rather than asking a team to adopt an entirely new, Python-centric stack.
Its plugin system lets existing business logic, written in C# or Java long before LLMs entered the picture, get exposed to a model as a callable tool, which matters a lot for large enterprises with substantial existing codebases they want an agent to act on rather than replace. Microsoft has positioned it alongside AutoGen, with Microsoft Agent Framework now intended as the eventual consolidation point for both projects.
It's free and open source under the MIT license, and its main audience, enterprise teams already committed to .NET or the Java ecosystem, sets it apart from frameworks that mostly assume a Python-first stack from the start.