Semantic Kernel

Semantic Kernel is an open-source SDK from Microsoft that helps developers add LLM features and agents to applications. It supports plugins, planning, memory and multi-agent patterns, and works with Azure OpenAI, OpenAI and other providers.

It is a natural choice for .NET shops, since the C# version is first-class, and it integrates with the rest of the Microsoft stack. Microsoft is merging its ideas with AutoGen in a newer agent framework.

It is more structured than throwing prompts into raw API calls, which suits enterprise teams. Hobbyists on Python may find lighter libraries quicker.