agent-as-function-tool

Using an agent as a function tool

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

This tutorial shows you how to use an agent as a function tool, so that one agent can call another agent as a tool.

Prerequisites

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

Create and use an agent as a function tool

You can use an AIAgent as a function tool by calling .AsAIFunction() on the agent and providing it as a tool to another agent. This allows you to compose agents and build more advanced workflows.

First, create a function tool as a C# method, and decorate it with descriptions if needed. This tool will be used by your agent that's exposed as a function.

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.";

Create an AIAgent that uses the function tool.

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

AIAgent weatherAgent = new AzureOpenAIClient(
    new Uri("https://<myresource>.openai.azure.com"),
    new AzureCliCredential())
     .GetChatClient("gpt-4o-mini")
     .AsAIAgent(
        instructions: "You answer questions about the weather.",
        name: "WeatherAgent",
        description: "An agent that answers questions about the weather.",
        tools: [AIFunctionFactory.Create(GetWeather)]);

Now, create a main agent and provide the weatherAgent as a function tool by calling .AsAIFunction() to convert weatherAgent to a function tool.

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