chore: import upstream snapshot with attribution

dotnet/samples/02-agents/Agents/Agent_Step09_AsFunctionTool/Program.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+// Agent as Function Tool — Use one agent as a tool for another
+//
+// This sample shows how to create an AI agent and expose it as a
+// function tool that another agent can call.
+
+using System.ComponentModel;
+using Azure.AI.Projects;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+
+var endpoint = Environment.GetEnvironmentVariable("FOUNDRY_PROJECT_ENDPOINT") ?? throw new InvalidOperationException("FOUNDRY_PROJECT_ENDPOINT is not set.");
+var deploymentName = Environment.GetEnvironmentVariable("FOUNDRY_MODEL") ?? "gpt-5.4-mini";
+
+[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 the agent and provide the function tool to it.
+// WARNING: DefaultAzureCredential is convenient for development but requires careful consideration in production.
+// In production, consider using a specific credential (e.g., ManagedIdentityCredential) to avoid
+// latency issues, unintended credential probing, and potential security risks from fallback mechanisms.
+AIProjectClient aiProjectClient = new(new Uri(endpoint), new DefaultAzureCredential());
+
+AIAgent weatherAgent = aiProjectClient
+     .AsAIAgent(
+        model: deploymentName,
+        instructions: "You answer questions about the weather.",
+        name: "WeatherAgent",
+        description: "An agent that answers questions about the weather.",
+        tools: [AIFunctionFactory.Create(GetWeather)]);
+
+// Create the main agent, and provide the weather agent as a function tool.
+AIAgent agent = aiProjectClient
+    .AsAIAgent(
+        model: deploymentName,
+        instructions: "You are a helpful assistant who responds in French.",
+        tools: [weatherAgent.AsAIFunction()]);
+
+// Invoke the agent and output the text result.
+Console.WriteLine(await agent.RunAsync("What is the weather like in Amsterdam?"));