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Why use function calling with Semantic Kernel Text Search?

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In the previous Retrieval-Augmented Generation (RAG) based samples the user ask has been used as the search query when retrieving relevant information. The user ask could be long and may span multiple topics or there may be multiple different search implementations available which provide specialized results. For either of these scenarios it can be useful to allow the AI model to extract the search query or queries from the user ask and use function calling to retrieve the relevant information it needs.

Tip

To run the samples shown on this page go to GettingStartedWithTextSearch/Step3_Search_With_FunctionCalling.cs.

Function calling with Bing text search

Tip

The samples in this section use an IFunctionInvocationFilter filter to log the function that the model calls and what parameters it sends. It is interesting to see what the model uses as a search query when calling the SearchPlugin.

Here is the IFunctionInvocationFilter filter implementation.

private sealed class FunctionInvocationFilter(TextWriter output) : IFunctionInvocationFilter
{
    public async Task OnFunctionInvocationAsync(FunctionInvocationContext context, Func<FunctionInvocationContext, Task> next)
    {
        if (context.Function.PluginName == "SearchPlugin")
        {
            output.WriteLine($"{context.Function.Name}:{JsonSerializer.Serialize(context.Arguments)}\n");
        }
        await next(context);
    }
}

The sample below creates a SearchPlugin using Bing web search. This plugin will be advertised to the AI model for use with automatic function calling, using the FunctionChoiceBehavior in the prompt execution settings. When you run this sample check the console output to see what the model used as the search query.

using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Connectors.OpenAI;
using Microsoft.SemanticKernel.Data;
using Microsoft.SemanticKernel.Plugins.Web.Bing;

// Create a kernel with OpenAI chat completion
IKernelBuilder kernelBuilder = Kernel.CreateBuilder();
kernelBuilder.AddOpenAIChatCompletion(
        modelId: "gpt-4o",
        apiKey: "<Your OpenAI API Key>");
kernelBuilder.Services.AddSingleton<ITestOutputHelper>(output);
kernelBuilder.Services.AddSingleton<IFunctionInvocationFilter, FunctionInvocationFilter>();
Kernel kernel = kernelBuilder.Build();

// Create a search service with Bing search
var textSearch = new BingTextSearch(apiKey: "<Your Bing API Key>");

// Build a text search plugin with Bing search and add to the kernel
var searchPlugin = textSearch.CreateWithSearch("SearchPlugin");
kernel.Plugins.Add(searchPlugin);

// Invoke prompt and use text search plugin to provide grounding information
OpenAIPromptExecutionSettings settings = new() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() };
KernelArguments arguments = new(settings);
Console.WriteLine(await kernel.InvokePromptAsync("What is the Semantic Kernel?", arguments));

Function calling with Bing text search and citations

The sample below includes the required changes to include citations:

  1. Use CreateWithGetTextSearchResults to create the SearchPlugin, this will include the link to the original source of the information.
  2. Modify the prompt to instruct the model to include citations in it's response.
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Connectors.OpenAI;
using Microsoft.SemanticKernel.Data;
using Microsoft.SemanticKernel.Plugins.Web.Bing;

// Create a kernel with OpenAI chat completion
IKernelBuilder kernelBuilder = Kernel.CreateBuilder();
kernelBuilder.AddOpenAIChatCompletion(
        modelId: "gpt-4o",
        apiKey: "<Your OpenAI API Key>");
kernelBuilder.Services.AddSingleton<ITestOutputHelper>(output);
kernelBuilder.Services.AddSingleton<IFunctionInvocationFilter, FunctionInvocationFilter>();
Kernel kernel = kernelBuilder.Build();

// Create a search service with Bing search
var textSearch = new BingTextSearch(apiKey: "<Your Bing API Key>");

// Build a text search plugin with Bing search and add to the kernel
var searchPlugin = textSearch.CreateWithGetTextSearchResults("SearchPlugin");
kernel.Plugins.Add(searchPlugin);

// Invoke prompt and use text search plugin to provide grounding information
OpenAIPromptExecutionSettings settings = new() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() };
KernelArguments arguments = new(settings);
Console.WriteLine(await kernel.InvokePromptAsync("What is the Semantic Kernel? Include citations to the relevant information where it is referenced in the response.", arguments));

Function calling with Bing text search and filtering

The final sample in this section shows how to use a filter with function calling. For this sample only search results from the Microsoft Developer Blogs site will be included. An instance of TextSearchFilter is created and an equality clause is added to match the devblogs.microsoft.com site. Ths filter will be used when the function is invoked in response to a function calling request from the model.

using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Connectors.OpenAI;
using Microsoft.SemanticKernel.Data;
using Microsoft.SemanticKernel.Plugins.Web.Bing;

// Create a kernel with OpenAI chat completion
IKernelBuilder kernelBuilder = Kernel.CreateBuilder();
kernelBuilder.AddOpenAIChatCompletion(
        modelId: "gpt-4o",
        apiKey: "<Your OpenAI API Key>");
kernelBuilder.Services.AddSingleton<ITestOutputHelper>(output);
kernelBuilder.Services.AddSingleton<IFunctionInvocationFilter, FunctionInvocationFilter>();
Kernel kernel = kernelBuilder.Build();

// Create a search service with Bing search
var textSearch = new BingTextSearch(apiKey: "<Your Bing API Key>");

// Build a text search plugin with Bing search and add to the kernel
var filter = new TextSearchFilter().Equality("site", "devblogs.microsoft.com");
var searchOptions = new TextSearchOptions() { Filter = filter };
var searchPlugin = KernelPluginFactory.CreateFromFunctions(
    "SearchPlugin", "Search Microsoft Developer Blogs site only",
    [textSearch.CreateGetTextSearchResults(searchOptions: searchOptions)]);
kernel.Plugins.Add(searchPlugin);

// Invoke prompt and use text search plugin to provide grounding information
OpenAIPromptExecutionSettings settings = new() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() };
KernelArguments arguments = new(settings);
Console.WriteLine(await kernel.InvokePromptAsync("What is the Semantic Kernel? Include citations to the relevant information where it is referenced in the response.", arguments));

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Next steps

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