function-tools

Using function tools with an agent

This tutorial step shows you how to use function tools with an agent, where the agent is built on the Azure OpenAI Chat Completion service.

::: zone pivot="programming-language-csharp"

[!IMPORTANT] Not all agent types support function tools. Some might only support custom built-in tools, without allowing the caller to provide their own functions. This step uses a ChatClientAgent, which does support function tools.

Prerequisites

For prerequisites and installing NuGet packages, see the Create and run a simple agent step in this tutorial.

Create the agent with function tools

Function tools are just custom code that you want the agent to be able to call when needed. You can turn any C# method into a function tool, by using the AIFunctionFactory.Create method to create an AIFunction instance from the method.

If you need to provide additional descriptions about the function or its parameters to the agent, so that it can more accurately choose between different functions, you can use the System.ComponentModel.DescriptionAttribute attribute on the method and its parameters.

Here is an example of a simple function tool that fakes getting the weather for a given location. It is decorated with description attributes to provide additional descriptions about itself and its location parameter to the agent.

using System.ComponentModel;

[Description("Get the weather for a given location.")]
static string GetWeather([Description("The location to get the weather for.")] string location)
    => $"The weather in {location} is cloudy with a high of 15°C.";

When creating the agent, you can now provide the function tool to the agent, by passing a list of tools to the AsAIAgent method.

using System;
using Azure.AI.OpenAI;
using Azure.Identity;
using Microsoft.Agents.AI;
using Microsoft.Extensions.AI;
using OpenAI;

AIAgent agent = new AzureOpenAIClient(
    new Uri("https://<myresource>.openai.azure.com"),
    new AzureCliCredential())
     .GetChatClient("gpt-4o-mini")
     .AsAIAgent(instructions: "You are a helpful assistant", tools: [AIFunctionFactory.Create(GetWeather)]);