
semantic-kernel
An agent SDK with unusual depth, still maintained, though new capability now lands in its successor Agent Framework.
What is semantic-kernel?
Semantic Kernel puts a kernel at the centre of the application: a container you register model connections and plugins into, which the agents you build then draw on. Mark ordinary methods as kernel functions and the model can call them, import a whole API from an OpenAPI description, wrap filters around a call to log, cache, redact or stop it, and hand a conversation between several specialised agents. The trade-off is direction rather than quality. Microsoft has named Agent Framework the successor and says the majority of new features will be built there, so this codebase keeps getting fixes and will see some existing features reach general availability, but few new ideas. It suits a team extending something already written against it far better than a project starting from nothing today.
What can you do with semantic-kernel?
- One kernel holds the model connections and the tools — You register chat model connections and plugins into a kernel, and the agents you build draw on it. Moving from OpenAI to Azure OpenAI, Ollama or Hugging Face is a change to that registration rather than to the agent code around it.
- Any method in your code becomes a tool the model can call — Tag a method as a kernel function and its name, description and parameter types become the tool description sent to the model. A whole API can be imported from an OpenAPI description; importing tools from an MCP server, and publishing your own functions as an MCP server, are documented for Python only, with .NET served by samples in the repository while its documentation still says it is coming.
- Three places to intercept what the model does — A prompt render filter runs before a prompt is assembled, a function invocation filter runs around any kernel function call, and an auto function invocation filter runs inside the automatic tool-calling loop. The documented uses are redacting personal data, caching answers, retrying against a different model, and stopping the loop once the answer is good enough. Filters hang off the kernel, so calling a chat completion service directly without passing the kernel skips them.
- Five named patterns for several agents working together — Concurrent broadcasts one task to every agent, Sequential passes each result to the next, Handoff moves control between agents as the context demands, Group Chat runs a conversation under a manager, and Magentic widens that group chat to open-ended tasks. All five share one construct-and-invoke interface, so changing how agents collaborate does not mean rewriting them.
- Conversation history stays local or lives in a hosted service — A thread carries the state of one conversation, either held in your own process or kept server-side by a service such as the Azure AI Agent service inside a Microsoft Foundry project. A service-backed agent accepts only its own matching thread type and raises an error immediately if you pair it with another.
- The vector search half can be used on its own — Annotate a data model to declare its key, its filterable fields and its vectors, and roughly fifteen databases — Azure AI Search, Postgres, Qdrant, Redis, Weaviate, Pinecone, an in-memory store and more — sit behind one API. The documentation states these implementations do not depend on the core Semantic Kernel stack, and in .NET the abstractions ship as a separate package. It also lists a maintainer per connector: Oracle, Elastic and Couchbase maintain their own rather than Microsoft.
Before you choose semantic-kernel
- Microsoft names Agent Framework the successor: Semantic Kernel v1.x is promised critical bug and security fixes for at least a year past Agent Framework's April 2026 general availability, and new work goes there.
- Multi-agent orchestration and the Process Framework are still marked experimental, and in .NET ship only as prerelease packages; the earlier group-chat API is no longer maintained, though a migration guide is provided.
Star history
17 Aug to 28 Aug · +51
Frequently asked questions
Is semantic-kernel free for commercial use?
semantic-kernel is released under the MIT licence — OSI-approved open source, which permits commercial use.
How can semantic-kernel be deployed?
semantic-kernel is available as Self-hosted / Runs locally.
Documentation
Reproduced from the microsoft/semantic-kernel README, published under MIT. Read the original ↗
Semantic Kernel
[!IMPORTANT] Semantic Kernel is now Microsoft Agent Framework! Microsoft Agent Framework (MAF) is the enterprise‑ready successor to Semantic Kernel. Microsoft Agent Framework is now available at version 1.0 as a production-ready release: stable APIs, and a commitment to long-term support. Whether you’re building a single assistant or orchestrating a fleet of specialized agents, Microsoft Agent Framework 1.0 gives you enterprise-grade multi-agent orchestration, multi-provider model support, and cross-runtime interoperability via A2A and MCP.
Learn more about Semantic Kernel and Agent Framework here: Semantic Kernel and Microsoft Agent Framework on the Agent Framework blog, and try out the Semantic Kernel migration guide.
Build intelligent AI agents and multi-agent systems with this enterprise-ready orchestration framework
What is Semantic Kernel?
Semantic Kernel is a model-agnostic SDK that empowers developers to build, orchestrate, and deploy AI agents and multi-agent systems. Whether you’re building a simple chatbot or a complex multi-agent workflow, Semantic Kernel provides the tools you need with enterprise-grade reliability and flexibility.
System Requirements
- Python: 3.10+
- .NET: .NET 10.0+
- Java: JDK 17+
- OS Support: Windows, macOS, Linux
Key Features
- Model Flexibility: Connect to any LLM with built-in support for OpenAI, Azure OpenAI, Hugging Face, NVidia and more
- Agent Framework: Build modular AI agents with access to tools/plugins, memory, and planning capabilities
- Multi-Agent Systems: Orchestrate complex workflows with collaborating specialist agents
- Plugin Ecosystem: Extend with native code functions, prompt templates, OpenAPI specs, or Model Context Protocol (MCP)
- Vector DB Support: Seamless integration with Azure AI Search, Elasticsearch, Chroma, and more
- Multimodal Support: Process text, vision, and audio inputs
- Local Deployment: Run with Ollama, LMStudio, or ONNX
- Process Framework: Model complex business processes with a structured workflow approach
- Enterprise Ready: Built for observability, security, and stable APIs
Installation
First, set the environment variable for your AI Services:
Azure OpenAI:
export AZURE_OPENAI_API_KEY=AAA....
or OpenAI directly:
export OPENAI_API_KEY=sk-...
Python
pip install semantic-kernel
.NET
dotnet add package Microsoft.SemanticKernel
dotnet add package Microsoft.SemanticKernel.Agents.Core
Java
See semantic-kernel-java build for instructions.
Quickstart
Basic Agent - Python
Create a simple assistant that responds to user prompts:
import asyncio
from semantic_kernel.agents import ChatCompletionAgent
from semantic_kernel.connectors.ai.open_ai import AzureChatCompletion
async def main():
# Initialize a chat agent with basic instructions
agent = ChatCompletionAgent(
service=AzureChatCompletion(),
name="SK-Assistant",
instructions="You are a helpful assistant.",
)
# Get a response to a user message
response = await agent.get_response(messages="Write a haiku about Semantic Kernel.")
print(response.content)
asyncio.run(main())
# Output:
# Language's essence,
# Semantic threads intertwine,
# Meaning's core revealed.
Basic Agent - .NET
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Agents;
var builder = Kernel.CreateBuilder();
builder.AddAzureOpenAIChatCompletion(
Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT"),
Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT"),
Environment.GetEnvironmentVariable("AZURE_OPENAI_API_KEY")
);
var kernel = builder.Build();
ChatCompletionAgent agent =
new()
{
Name = "SK-Agent",
Instructions = "You are a helpful assistant.",
Kernel = kernel,
};
await foreach (AgentResponseItem<ChatMessageContent> response
in agent.InvokeAsync("Write a haiku about Semantic Kernel."))
{
Console.WriteLine(response.Message);
}
// Output:
// Language's essence,
// Semantic threads intertwine,
// Meaning's core revealed.
Agent with Plugins - Python
Enhance your agent with custom tools (plugins) and structured output:
import asyncio
from typing import Annotated
from pydantic import BaseModel
from semantic_kernel.agents import ChatCompletionAgent
from semantic_kernel.connectors.ai.open_ai import AzureChatCompletion, OpenAIChatPromptExecutionSettings
from semantic_kernel.functions import kernel_function, KernelArguments
class MenuPlugin:
@kernel_function(description="Provides a list of specials from the menu.")
def get_specials(self) -> Annotated[str, "Returns the specials from the menu."]:
return """
Special Soup: Clam Chowder
Special Salad: Cobb Salad
Special Drink: Chai Tea
"""
@kernel_function(description="Provides the price of the requested menu item.")
def get_item_price(
self, menu_item: Annotated[str, "The name of the menu item."]
) -> Annotated[str, "Returns the price of the menu item."]:
return "$9.99"
class MenuItem(BaseModel):
price: float
name: str
async def main():
# Configure structured output format
settings = OpenAIChatPromptExecutionSettings()
settings.response_format = MenuItem
# Create agent with plugin and settings
agent = ChatCompletionAgent(
service=AzureChatCompletion(),
name="SK-Assistant",
instructions="You are a helpful assistant.",
plugins=[MenuPlugin()],
arguments=KernelArguments(settings)
)
response = await agent.get_response(messages="What is the price of the soup special?")
print(response.content)
# Output:
# The price of the Clam Chowder, which is the soup special, is $9.99.
asyncio.run(main())
Agent with Plugin - .NET
using System.ComponentModel;
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Agents;
using Microsoft.SemanticKernel.ChatCompletion;
var builder = Kernel.CreateBuilder();
builder.AddAzureOpenAIChatCompletion(
Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT"),
Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT"),
Environment.GetEnvironmentVariable("AZURE_OPENAI_API_KEY")
);
var kernel = builder.Build();
kernel.Plugins.Add(KernelPluginFactory.CreateFromType<MenuPlugin>());
ChatCompletionAgent agent =
new()
{
Name = "SK-Assistant",
Instructions = "You are a helpful assistant.",
Kernel = kernel,
Arguments = new KernelArguments(new PromptExecutionSettings() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() })
};
await foreach (AgentResponseItem<ChatMessageContent> response
in agent.InvokeAsync("What is the price of the soup special?"))
{
Console.WriteLine(response.Message);
}
sealed class MenuPlugin
{
[KernelFunction, Description("Provides a list of specials from the menu.")]
public string GetSpecials() =>
"""
Special Soup: Clam Chowder
Special Salad: Cobb Salad
Special Drink: Chai Tea
""";
[KernelFunction, Description("Provides the price of the requested menu item.")]
public string GetItemPrice(
[Description("The name of the menu item.")]
string menuItem) =>
"$9.99";
}
Multi-Agent System - Python
Build a system of specialized agents that can collaborate:
import asyncio
from semantic_kernel.agents import ChatCompletionAgent, ChatHistoryAgentThread
from semantic_kernel.connectors.ai.open_ai import AzureChatCompletion, OpenAIChatCompletion
billing_agent = ChatCompletionAgent(
service=AzureChatCompletion(),
name="BillingAgent",
instructions="You handle billing issues like charges, payment methods, cycles, fees, discrepancies, and payment failures."
)
refund_agent = ChatCompletionAgent(
service=AzureChatCompletion(),
name="RefundAgent",
instructions="Assist users with refund inquiries, including eligibility, policies, processing, and status updates.",
)
triage_agent = ChatCompletionAgent(
service=OpenAIChatCompletion(),
name="TriageAgent",
instructions="Evaluate user requests and forward them to BillingAgent or RefundAgent for targeted assistance."
" Provide the full answer to the user containing any information from the agents",
plugins=[billing_agent, refund_agent],
)
thread: ChatHistoryAgentThread = None
async def main() -> None:
print("Welcome to the chat bot!\n Type 'exit' to exit.\n Try to get some billing or refund help.")
while True:
user_input = input("User:> ")
if user_input.lower().strip() == "exit":
print("\n\nExiting chat...")
return False
response = await triage_agent.get_response(
messages=user_input,
thread=thread,
)
if response:
print(f"Agent :> {response}")
# Agent :> I understand that you were charged twice for your subscription last month, and I'm here to assist you with resolving this issue. Here’s what we need to do next:
# 1. **Billing Inquiry**:
# - Please provide the email address or account number associated with your subscription, the date(s) of the charges, and the amount charged. This will allow the billing team to investigate the discrepancy in the charges.
# 2. **Refund Process**:
# - For the refund, please confirm your subscription type and the email address associated with your account.
# - Provide the dates and transaction IDs for the charges you believe were duplicated.
# Once we have these details, we will be able to:
# - Check your billing history for any discrepancies.
# - Confirm any duplicate charges.
# - Initiate a refund for the duplicate payment if it qualifies. The refund process usually takes 5-10 business days after approval.
# Please provide the necessary details so we can proceed with resolving this issue for you.
if __name__ == "__main__":
asyncio.run(main())
Where to Go Next
- 📖 Try our Getting Started Guide or learn about Building Agents
- 🔌 Explore over 100 Detailed Samples
- 💡 Learn about core Semantic Kernel Concepts
API References
Troubleshooting
Common Issues
- Authentication Errors: Check that your API key environment variables are correctly set
- Model Availability: Verify your Azure OpenAI deployment or OpenAI model access
Getting Help
- Check our GitHub issues for known problems
- Search the Discord community for solutions
- Include your SDK version and full error messages when asking for help
Join the community
We welcome your contributions and suggestions to the SK community! One of the easiest ways to participate is to engage in discussions in the GitHub repository. Bug reports and fixes are welcome!
For new features, components, or extensions, please open an issue and discuss with us before sending a PR. This is to avoid rejection as we might be taking the core in a different direction, but also to consider the impact on the larger ecosystem.
To learn more and get started:
-
Read the documentation
-
Learn how to contribute to the project
-
Ask questions in the GitHub discussions
-
Ask questions in the Discord community
-
Follow the team on our blog