chore: import upstream snapshot with attribution

dotnet/samples/02-agents/A2A/A2AAgent_AsFunctionTools/Program.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample shows how to represent an A2A agent as a set of function tools, where each function tool
+// corresponds to a skill of the A2A agent, and register these function tools with another AI agent so
+// it can leverage the A2A agent's skills.
+
+using System.Text.RegularExpressions;
+using A2A;
+using Azure.AI.OpenAI;
+using Azure.Identity;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+using OpenAI.Chat;
+
+var endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? throw new InvalidOperationException("AZURE_OPENAI_ENDPOINT is not set.");
+var deploymentName = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT_NAME") ?? "gpt-5.4-mini";
+var a2aAgentHost = Environment.GetEnvironmentVariable("A2A_AGENT_HOST") ?? throw new InvalidOperationException("A2A_AGENT_HOST is not set.");
+
+// Initialize an A2ACardResolver to get an A2A agent card.
+A2ACardResolver agentCardResolver = new(new Uri(a2aAgentHost));
+
+// Get the agent card
+AgentCard agentCard = await agentCardResolver.GetAgentCardAsync();
+
+// Create an instance of the AIAgent for an existing A2A agent specified by the agent card.
+AIAgent a2aAgent = agentCard.AsAIAgent();
+
+// Create the main agent, and provide the a2a agent skills as a function tools.
+// 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.
+AIAgent agent = new AzureOpenAIClient(
+    new Uri(endpoint),
+    new DefaultAzureCredential())
+    .GetChatClient(deploymentName)
+    .AsAIAgent(
+        instructions: "You are a helpful assistant that helps people with travel planning.",
+        tools: [.. CreateFunctionTools(a2aAgent, agentCard)]
+    );
+
+// Invoke the agent and output the text result.
+Console.WriteLine(await agent.RunAsync("Plan a route from '1600 Amphitheatre Parkway, Mountain View, CA' to 'San Francisco International Airport' avoiding tolls"));
+
+static IEnumerable<AIFunction> CreateFunctionTools(AIAgent a2aAgent, AgentCard agentCard)
+{
+    foreach (var skill in agentCard.Skills)
+    {
+        // A2A agent skills don't have schemas describing the expected shape of their inputs and outputs. 
+        // Schemas can be beneficial for AI models to better understand the skill's contract, generate 
+        // the skill's input accordingly and to know what to expect in the skill's output.
+        // However, the A2A specification defines properties such as name, description, tags, examples, 
+        // inputModes, and outputModes to provide context about the skill's purpose, capabilities, usage, 
+        // and supported MIME types. These properties are added to the function tool description to help 
+        // the model determine the appropriate shape of the skill's input and output.
+        AIFunctionFactoryOptions options = new()
+        {
+            Name = FunctionNameSanitizer.Sanitize(skill.Name),
+            Description = $$"""
+            {
+                "description": "{{skill.Description}}",
+                "tags": "[{{string.Join(", ", skill.Tags ?? [])}}]",
+                "examples": "[{{string.Join(", ", skill.Examples ?? [])}}]",
+                "inputModes": "[{{string.Join(", ", skill.InputModes ?? [])}}]",
+                "outputModes": "[{{string.Join(", ", skill.OutputModes ?? [])}}]"
+            }
+            """,
+        };
+
+        yield return AIFunctionFactory.Create(RunAgentAsync, options);
+    }
+
+    async Task<string> RunAgentAsync(string input, CancellationToken cancellationToken)
+    {
+        var response = await a2aAgent.RunAsync(input, cancellationToken: cancellationToken).ConfigureAwait(false);
+
+        return response.Text;
+    }
+}
+
+internal static partial class FunctionNameSanitizer
+{
+    public static string Sanitize(string name)
+    {
+        return InvalidNameCharsRegex().Replace(name, "_");
+    }
+
+    [GeneratedRegex("[^0-9A-Za-z]+")]
+    private static partial Regex InvalidNameCharsRegex();
+}