chore: import upstream snapshot with attribution

dotnet/samples/02-agents/A2A/A2AAgent_AsFunctionTools/A2AAgent_AsFunctionTools.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="A2A" />
+    <PackageReference Include="Azure.AI.OpenAI" />
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.A2A\Microsoft.Agents.AI.A2A.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.OpenAI\Microsoft.Agents.AI.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

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();
+}

dotnet/samples/02-agents/A2A/A2AAgent_AsFunctionTools/README.md

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+# A2A Agent as Function Tools
+
+This sample demonstrates 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.
+
+# Prerequisites
+
+Before you begin, ensure you have the following prerequisites:
+
+- .NET 10 SDK or later
+- Access to the A2A agent host service
+
+**Note**: These samples need to be run against a valid A2A server. If no A2A server is available, they can be run against the echo-agent that can be 
+spun up locally by following the guidelines at: https://github.com/a2aproject/a2a-dotnet/blob/main/samples/AgentServer/README.md
+
+Set the following environment variables:
+
+```powershell
+$env:A2A_AGENT_HOST="https://your-a2a-agent-host" # Replace with your A2A agent host endpoint
+$env:AZURE_OPENAI_ENDPOINT="https://your-resource.openai.azure.com/" # Replace with your Azure OpenAI resource endpoint
+$env:AZURE_OPENAI_DEPLOYMENT_NAME="gpt-5.4-mini"  # Optional, defaults to gpt-5.4-mini
+```