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Exploring the Semantic Kernel ChatCompletionAgent

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Detailed API documentation related to this discussion is available at:

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Detailed API documentation related to this discussion is available at:

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Detailed API documentation related to this discussion is available at:

Chat Completion in Semantic Kernel

Chat Completion is fundamentally a protocol for a chat-based interaction with an AI model where the chat-history is maintained and presented to the model with each request. Semantic Kernel AI services offer a unified framework for integrating the chat-completion capabilities of various AI models.

A ChatCompletionAgent can leverage any of these AI services to generate responses, whether directed to a user or another agent.

Preparing Your Development Environment

To proceed with developing an ChatCompletionAgent, configure your development environment with the appropriate packages.

Add the Microsoft.SemanticKernel.Agents.Core package to your project:

dotnet add package Microsoft.SemanticKernel.Agents.Core --prerelease

Install the semantic-kernel package:

pip install semantic-kernel

Important

Depending upon which AI Service you use as part of the ChatCompletionAgent, you may need to install extra packages. Please check for the required extra on the following page

<dependency>
    <groupId>com.microsoft.semantic-kernel</groupId>
    <artifactId>semantickernel-agents-core</artifactId>
    <version>[LATEST]</version>
</dependency>

Creating a ChatCompletionAgent

A ChatCompletionAgent is fundamentally based on an AI services. As such, creating a ChatCompletionAgent starts with creating a Kernel instance that contains one or more chat-completion services and then instantiating the agent with a reference to that Kernel instance.

// Initialize a Kernel with a chat-completion service
IKernelBuilder builder = Kernel.CreateBuilder();

builder.AddAzureOpenAIChatCompletion(/*<...configuration parameters>*/);

Kernel kernel = builder.Build();

// Create the agent
ChatCompletionAgent agent =
    new()
    {
        Name = "SummarizationAgent",
        Instructions = "Summarize user input",
        Kernel = kernel
    };

There are two ways to create a ChatCompletionAgent:

1. By providing the chat completion service directly

from semantic_kernel.agents import ChatCompletionAgent

# Create the agent by directly providing the chat completion service
agent = ChatCompletionAgent(
    service=AzureChatCompletion(),  # your chat completion service instance
    name="<agent name>",
    instructions="<agent instructions>",
)

2. By creating a Kernel first, adding the service to it, then providing the kernel

# Define the kernel
kernel = Kernel()

# Add the chat completion service to the kernel
kernel.add_service(AzureChatCompletion())

# Create the agent using the kernel
agent = ChatCompletionAgent(
  kernel=kernel, 
  name="<agent name>", 
  instructions="<agent instructions>",
)

The first method is useful when you already have a chat completion service ready. The second method is beneficial when you need a kernel that manages multiple services or additional functionalities.

// Initialize a Kernel with a chat-completion service
var chatCompletion = OpenAIChatCompletion.builder()
        .withOpenAIAsyncClient(client) // OpenAIAsyncClient with configuration parameters
        .withModelId(MODEL_ID)
        .build();

var kernel = Kernel.builder()
        .withAIService(ChatCompletionService.class, chatCompletion)
        .build();

// Create the agent
var agent = ChatCompletionAgent.builder()
        .withKernel(kernel)
        .build();

AI Service Selection

No different from using Semantic Kernel AI services directly, a ChatCompletionAgent supports the specification of a service-selector. A service-selector identifies which AI service to target when the Kernel contains more than one.

Note

If multiple AI services are present and no service-selector is provided, the same default logic is applied for the agent that you'd find when using an AI services outside of the Agent Framework

IKernelBuilder builder = Kernel.CreateBuilder();

// Initialize multiple chat-completion services.
builder.AddAzureOpenAIChatCompletion(/*<...service configuration>*/, serviceId: "service-1");
builder.AddAzureOpenAIChatCompletion(/*<...service configuration>*/, serviceId: "service-2");

Kernel kernel = builder.Build();

ChatCompletionAgent agent =
    new()
    {
        Name = "<agent name>",
        Instructions = "<agent instructions>",
        Kernel = kernel,
        Arguments = // Specify the service-identifier via the KernelArguments
          new KernelArguments(
            new OpenAIPromptExecutionSettings() 
            { 
              ServiceId = "service-2" // The target service-identifier.
            })
    };

from semantic_kernel.connectors.ai.open_ai import (
    AzureChatCompletion,
    AzureChatPromptExecutionSettings,
)

# Define the Kernel
kernel = Kernel()

# Add the AzureChatCompletion AI Service to the Kernel
kernel.add_service(AzureChatCompletion(service_id="service1"))
kernel.add_service(AzureChatCompletion(service_id="service2"))

settings = AzureChatPromptExecutionSettings(service_id="service2")

# Create the agent
agent = ChatCompletionAgent(
  kernel=kernel, 
  name="<agent name>", 
  instructions="<agent instructions>",
  arguments=KernelArguments(settings=settings)
)

Feature currently unavailable in Java.

Conversing with ChatCompletionAgent

Conversing with your ChatCompletionAgent is based on a ChatHistory instance, no different from interacting with a Chat Completion AI service.

You can simply invoke the agent with your user message.

// Define agent
ChatCompletionAgent agent = ...;

// Generate the agent response(s)
await foreach (ChatMessageContent response in agent.InvokeAsync(new ChatMessageContent(AuthorRole.User, "<user input>")))
{
  // Process agent response(s)...
}

You can also use an AgentThread to have a conversation with your agent. Here we are using a ChatHistoryAgentThread.

The ChatHistoryAgentThread can also take an optional ChatHistory object as input, via its constructor, if resuming a previous conversation. (not shown)

// Define agent
ChatCompletionAgent agent = ...;

AgentThread thread = new ChatHistoryAgentThread();

// Generate the agent response(s)
await foreach (ChatMessageContent response in agent.InvokeAsync(new ChatMessageContent(AuthorRole.User, "<user input>"), thread))
{
  // Process agent response(s)...
}

There are multiple ways to converse with a ChatCompletionAgent.

The easiest is to call and await get_response:

# Define agent
agent = ChatCompletionAgent(...)

# Generate the agent response
response = await agent.get_response(messages="user input")
# response is an `AgentResponseItem[ChatMessageContent]` object

If you want the agent to maintain conversation history between invocations, you can pass it a ChatHistoryAgentThread as follows:


# Define agent
agent = ChatCompletionAgent(...)

# Generate the agent response(s)
response = await agent.get_response(messages="user input")

# Generate another response, continuing the conversation thread from the first response.
response2 = await agent.get_response(messages="user input", thread=response.thread)
# process agent response(s)

Calling the invoke method returns an AsyncIterable of AgentResponseItem[ChatMessageContent].

# Define agent
agent = ChatCompletionAgent(...)

# Define the thread
thread = ChatHistoryAgentThread()

# Generate the agent response(s)
async for response in agent.invoke(messages="user input", thread=thread):
  # process agent response(s)

The ChatCompletionAgent also supports streaming in which the invoke_stream method returns an AsyncIterable of StreamingChatMessageContent:

# Define agent
agent = ChatCompletionAgent(...)

# Define the thread
thread = ChatHistoryAgentThread()

# Generate the agent response(s)
async for response in agent.invoke_stream(messages="user input", thread=thread):
  # process agent response(s)

ChatCompletionAgent agent = ...;

// Generate the agent response(s)
agent.invokeAsync(new ChatMessageContent<>(AuthorRole.USER, "<user input>")).block();

You can also use an AgentThread to have a conversation with your agent. Here we are using a ChatHistoryAgentThread.

The ChatHistoryAgentThread can also take a ChatHistory object as input, via its constructor, if resuming a previous conversation. (not shown)

// Define agent
ChatCompletionAgent agent = ...;

AgentThread thread = new ChatHistoryAgentThread();

// Generate the agent response(s)
agent.invokeAsync(new ChatMessageContent<>(AuthorRole.USER, "<user input>"), thread).block();

Handling Intermediate Messages with a ChatCompletionAgent

The Semantic Kernel ChatCompletionAgent is designed to invoke an agent that fulfills user queries or questions. During invocation, the agent may execute tools to derive the final answer. To access intermediate messages produced during this process, callers can supply a callback function that handles instances of FunctionCallContent or FunctionResultContent.

Callback documentation for the ChatCompletionAgent is coming soon.

Configuring the on_intermediate_message callback within agent.invoke(...) or agent.invoke_stream(...) allows the caller to receive intermediate messages generated during the process of formulating the agent's final response.

import asyncio
from typing import Annotated

from semantic_kernel.agents.chat_completion.chat_completion_agent import ChatCompletionAgent, ChatHistoryAgentThread
from semantic_kernel.connectors.ai.open_ai.services.azure_chat_completion import AzureChatCompletion
from semantic_kernel.contents import FunctionCallContent, FunctionResultContent
from semantic_kernel.contents.chat_message_content import ChatMessageContent
from semantic_kernel.functions import kernel_function


# Define a sample plugin for the sample
class MenuPlugin:
    """A sample Menu Plugin used for the concept sample."""

    @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"


# This callback function will be called for each intermediate message
# Which will allow one to handle FunctionCallContent and FunctionResultContent
# If the callback is not provided, the agent will return the final response
# with no intermediate tool call steps.
async def handle_intermediate_steps(message: ChatMessageContent) -> None:
    for item in message.items or []:
        if isinstance(item, FunctionCallContent):
            print(f"Function Call:> {item.name} with arguments: {item.arguments}")
        elif isinstance(item, FunctionResultContent):
            print(f"Function Result:> {item.result} for function: {item.name}")
        else:
            print(f"{message.role}: {message.content}")


async def main() -> None:
    agent = ChatCompletionAgent(
        service=AzureChatCompletion(),
        name="Assistant",
        instructions="Answer questions about the menu.",
        plugins=[MenuPlugin()],
    )

    # Create a thread for the agent
    # If no thread is provided, a new thread will be
    # created and returned with the initial response
    thread: ChatHistoryAgentThread = None

    user_inputs = [
        "Hello",
        "What is the special soup?",
        "How much does that cost?",
        "Thank you",
    ]

    for user_input in user_inputs:
        print(f"# User: '{user_input}'")
        async for response in agent.invoke(
            messages=user_input,
            thread=thread,
            on_intermediate_message=handle_intermediate_steps,
        ):
            print(f"# {response.role}: {response}")
            thread = response.thread


if __name__ == "__main__":
    asyncio.run(main())

The following demonstrates sample output from the agent invocation process:

User: 'Hello'
AuthorRole.ASSISTANT: Hi there! How can I assist you today?
User: 'What is the special soup?'
Function Call:> MenuPlugin-get_specials with arguments: {}
Function Result:> 
        Special Soup: Clam Chowder
        Special Salad: Cobb Salad
        Special Drink: Chai Tea
        for function: MenuPlugin-get_specials
AuthorRole.ASSISTANT: The special soup today is Clam Chowder. Would you like to know anything else from the menu?
User: 'How much does that cost?'
Function Call:> MenuPlugin-get_item_price with arguments: {"menu_item":"Clam Chowder"}
Function Result:> $9.99 for function: MenuPlugin-get_item_price
AuthorRole.ASSISTANT: The Clam Chowder costs $9.99. Would you like to know more about the menu or anything else?
User: 'Thank you'
AuthorRole.ASSISTANT: You're welcome! If you have any more questions, feel free to ask. Enjoy your day!

Feature currently unavailable in Java.

Declarative Spec

The documentation on using declarative specs is coming soon.

Important

This feature is in the experimental stage. Features at this stage are under development and subject to change before advancing to the preview or release candidate stage.

The ChatCompletionAgent can be instantiated directly from a YAML declarative specification. This approach allows you to define the agent’s core properties, instructions, and available functions (plugins) in a structured and portable way. By using YAML, you can describe the agent's name, description, instruction prompt, tool set, and model parameters in a single document, making the agent's configuration easily auditable and reproducible.

Note

Any tools or functions specified in the declarative YAML must already exist in the Kernel instance at the time the agent is created. The agent loader does not create new functions from the spec; instead, it looks up the referenced plugins and functions by their identifiers in the kernel. If a required plugin or function is not present in the kernel, an error will be raised during agent construction.

Example: Creating a ChatCompletionAgent from a YAML spec

import asyncio
from typing import Annotated

from semantic_kernel import Kernel
from semantic_kernel.agents import AgentRegistry, ChatHistoryAgentThread
from semantic_kernel.agents.chat_completion.chat_completion_agent import ChatCompletionAgent
from semantic_kernel.connectors.ai.open_ai import OpenAIChatCompletion
from semantic_kernel.functions import kernel_function

# Define a plugin with kernel functions
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"

# YAML spec for the agent
AGENT_YAML = """
type: chat_completion_agent
name: Assistant
description: A helpful assistant.
instructions: Answer the user's questions using the menu functions.
tools:
  - id: MenuPlugin.get_specials
    type: function
  - id: MenuPlugin.get_item_price
    type: function
model:
  options:
    temperature: 0.7
"""

USER_INPUTS = [
    "Hello",
    "What is the special soup?",
    "What does that cost?",
    "Thank you",
]

async def main():
    kernel = Kernel()
    kernel.add_plugin(MenuPlugin(), plugin_name="MenuPlugin")

    agent: ChatCompletionAgent = await AgentRegistry.create_from_yaml(
        AGENT_YAML, kernel=kernel, service=OpenAIChatCompletion()
    )

    thread: ChatHistoryAgentThread | None = None

    for user_input in USER_INPUTS:
        print(f"# User: {user_input}")
        response = await agent.get_response(user_input, thread=thread)
        print(f"# {response.name}: {response}")
        thread = response.thread

    await thread.delete() if thread else None

if __name__ == "__main__":
    asyncio.run(main())

This feature is unavailable.

How-To

For an end-to-end example for a ChatCompletionAgent, see:

Next Steps

Explore the Copilot Studio Agent