Semantic Kernel (28,422 Stars) 2026: Microsoft's SDK for Building AI Agents with Plugins and Memory

Semantic Kernel (28,422 stars) is Microsoft's open-source SDK for building AI agents and copilots with plugins, planners and memory. Here is how to get started in C# or Python.

💡 What You Will Learn

Semantic Kernel (28,422 stars) is Microsoft's open-source SDK for building AI agents and copilots with plugins, planners and memory. Here is how to get started in C# or Python.

📜 Table of Contents

• The short answer
• Core concepts
• Minimal example (C#)
• When to use Semantic Kernel vs LangChain
• Practical tips
• FAQ

The short answer

microsoft/semantic-kernel (28,422 stars, C#) is Microsoft's open-source SDK that lets you orchestrate AI agents in your applications. It provides plugins (skills), planners, memory, and connectors for models like OpenAI and Azure OpenAI - with first-class support in C#, Python, and Java.

Core concepts

Minimal example (C#)

using Microsoft.SemanticKernel;

var builder = Kernel.CreateBuilder();
builder.AddOpenAIChatCompletion("gpt-4o-mini", apiKey);

var kernel = builder.Build();

var result = await kernel.InvokePromptAsync(
    "Summarize this in one sentence: {{$input}}",
    new() { ["input"] = "..." });

Console.WriteLine(result);

Python version uses the same concepts:

from semantic_kernel import Kernel
kernel = Kernel()
kernel.add_service(OpenAIChatCompletion("gpt-4o-mini", api_key))

When to use Semantic Kernel vs LangChain

• Semantic Kernel shines when you live in the Microsoft/.NET ecosystem (C#, Azure).
• It is designed for enterprise copilots with structured plugins and governance.
• LangChain (143,505 stars) is broader with more community integrations; SK is more opinionated and Microsoft-centric.

Practical tips

• Start with plugins over planners - explicit function calls are easier to debug.
• Use the memory connectors (vector stores) to give your agent long-term context.
• Take advantage of the auto-function-calling to let models invoke your plugins safely.

FAQ

Is it free? Yes - MIT licensed open source.

Which languages? C#, Python, and Java are officially supported.

Does it work with local models? Yes - you can connect any OpenAI-compatible endpoint, including Ollama.

❓ FAQ

Is it free?

Yes - MIT licensed open source.

Which languages?

C#, Python, and Java are officially supported.

Does it work with local models?

Yes - you can connect any OpenAI-compatible endpoint, including Ollama.