.Net: Initial check-in for the A2A Agent implementation

dotnet/Directory.Packages.props

@@ -102,6 +102,9 @@
     <PackageVersion Include="System.Text.Json" Version="8.0.5" />
     <PackageVersion Include="System.ValueTuple" Version="4.6.1" />
     <PackageVersion Include="System.Threading.Tasks.Extensions" Version="4.6.3" />
+    <PackageVersion Include="SharpA2A.Core" Version="0.2.1-preview.1" />
+    <PackageVersion Include="SharpA2A.AspNetCore" Version="0.2.1-preview.1" />
+    <PackageVersion Include="System.CommandLine" Version="2.0.0-beta4.22272.1" />
     <!-- Tokenizers -->
     <PackageVersion Include="Microsoft.ML.Tokenizers" Version="1.0.2" />
     <PackageVersion Include="Microsoft.DeepDev.TokenizerLib" Version="1.3.3" />

dotnet/SK-dotnet.slnx

@@ -49,6 +49,10 @@
     <Project Path="samples/Demos/TimePlugin/TimePlugin.csproj" />
     <Project Path="samples/Demos/VectorStoreRAG/VectorStoreRAG.csproj" />
   </Folder>
+  <Folder Name="/samples/Demos/A2AClientServer/">
+    <Project Path="samples/Demos/A2AClientServer/A2AClient/A2AClient.csproj" />
+    <Project Path="samples/Demos/A2AClientServer/A2AServer/A2AServer.csproj" />
+  </Folder>
   <Folder Name="/samples/Demos/AgentFrameworkWithAspire/">
     <File Path="samples/Demos/AgentFrameworkWithAspire/README.md" />
     <Project Path="samples/Demos/AgentFrameworkWithAspire/ChatWithAgent.ApiService/ChatWithAgent.ApiService.csproj" />
@@ -87,6 +91,7 @@
     <Project Path="src/SemanticKernel.UnitTests/SemanticKernel.UnitTests.csproj" />
   </Folder>
   <Folder Name="/src/agents/">
+    <Project Path="src/Agents/A2A/Agents.A2A.csproj" />
     <Project Path="src/Agents/Abstractions/Agents.Abstractions.csproj" />
     <Project Path="src/Agents/AzureAI/Agents.AzureAI.csproj" />
     <Project Path="src/Agents/Bedrock/Agents.Bedrock.csproj" />

dotnet/samples/Demos/A2AClientServer/A2AClient/A2AClient.csproj

@@ -0,0 +1,24 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <UserSecretsId>5ee045b0-aea3-4f08-8d31-32d1a6f8fed0</UserSecretsId>
+    <NoWarn>$(NoWarn);CS1591;VSTHRD111;CA2007;SKEXP0110</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="SharpA2A.Core" />
+    <PackageReference Include="System.CommandLine" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Agents\A2A\Agents.A2A.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Agents\Core\Agents.Core.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Connectors\Connectors.OpenAI\Connectors.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/Demos/A2AClientServer/A2AClient/HostClientAgent.cs

@@ -0,0 +1,120 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.Extensions.Logging;
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.Agents;
+using Microsoft.SemanticKernel.Agents.A2A;
+using SharpA2A.Core;
+
+namespace A2A;
+
+internal sealed class HostClientAgent
+{
+    internal HostClientAgent(ILogger logger)
+    {
+        this._logger = logger;
+    }
+    internal async Task InitializeAgentAsync(string modelId, string apiKey, string[] agentUrls)
+    {
+        try
+        {
+            this._logger.LogInformation("Initializing Semantic Kernel agent with model: {ModelId}", modelId);
+
+            // Connect to the remote agents via A2A
+            var createAgentTasks = agentUrls.Select(agentUrl => this.CreateAgentAsync(agentUrl));
+            var agents = await Task.WhenAll(createAgentTasks);
+            var agentFunctions = agents.Select(agent => AgentKernelFunctionFactory.CreateFromAgent(agent)).ToList();
+            var agentPlugin = KernelPluginFactory.CreateFromFunctions("AgentPlugin", agentFunctions);
+
+            // Define the Host agent
+            var builder = Kernel.CreateBuilder();
+            builder.AddOpenAIChatCompletion(modelId, apiKey);
+            builder.Plugins.Add(agentPlugin);
+            var kernel = builder.Build();
+            kernel.FunctionInvocationFilters.Add(new ConsoleOutputFunctionInvocationFilter());
+
+            this.Agent = new ChatCompletionAgent()
+            {
+                Kernel = kernel,
+                Name = "HostClient",
+                Instructions =
+                    """
+                    You specialize in handling queries for users and using your tools to provide answers.
+                    """,
+                Arguments = new KernelArguments(new PromptExecutionSettings() { FunctionChoiceBehavior = FunctionChoiceBehavior.Auto() }),
+            };
+        }
+        catch (Exception ex)
+        {
+            this._logger.LogError(ex, "Failed to initialize HostClientAgent");
+            throw;
+        }
+    }
+
+    /// <summary>
+    /// The associated <see cref="Agent"/>
+    /// </summary>
+    public Agent? Agent { get; private set; }
+
+    #region private
+    private readonly ILogger _logger;
+
+    private async Task<A2AAgent> CreateAgentAsync(string agentUri)
+    {
+        var httpClient = new HttpClient
+        {
+            BaseAddress = new Uri(agentUri),
+            Timeout = TimeSpan.FromSeconds(60)
+        };
+
+        var client = new A2AClient(httpClient);
+        var cardResolver = new A2ACardResolver(httpClient);
+        var agentCard = await cardResolver.GetAgentCardAsync();
+
+        return new A2AAgent(client, agentCard!);
+    }
+    #endregion
+}
+
+internal sealed class ConsoleOutputFunctionInvocationFilter() : IFunctionInvocationFilter
+{
+    private static string IndentMultilineString(string multilineText, int indentLevel = 1, int spacesPerIndent = 4)
+    {
+        // Create the indentation string
+        var indentation = new string(' ', indentLevel * spacesPerIndent);
+
+        // Split the text into lines, add indentation, and rejoin
+        char[] NewLineChars = { '\r', '\n' };
+        string[] lines = multilineText.Split(NewLineChars, StringSplitOptions.None);
+
+        return string.Join(Environment.NewLine, lines.Select(line => indentation + line));
+    }
+    public async Task OnFunctionInvocationAsync(FunctionInvocationContext context, Func<FunctionInvocationContext, Task> next)
+    {
+        Console.ForegroundColor = ConsoleColor.DarkGray;
+
+        Console.WriteLine($"\nCalling Agent {context.Function.Name} with arguments:");
+        Console.ForegroundColor = ConsoleColor.Gray;
+
+        foreach (var kvp in context.Arguments)
+        {
+            Console.WriteLine(IndentMultilineString($"  {kvp.Key}: {kvp.Value}"));
+        }
+
+        await next(context);
+
+        if (context.Result.GetValue<object>() is ChatMessageContent[] chatMessages)
+        {
+            Console.ForegroundColor = ConsoleColor.DarkGray;
+
+            Console.WriteLine($"Response from Agent {context.Function.Name}:");
+            foreach (var message in chatMessages)
+            {
+                Console.ForegroundColor = ConsoleColor.Gray;
+
+                Console.WriteLine(IndentMultilineString($"{message}"));
+            }
+        }
+        Console.ResetColor();
+    }
+}

dotnet/samples/Demos/A2AClientServer/A2AClient/Program.cs

@@ -0,0 +1,89 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.CommandLine;
+using System.CommandLine.Invocation;
+using System.Reflection;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.Agents;
+
+namespace A2A;
+
+public static class Program
+{
+    public static async Task<int> Main(string[] args)
+    {
+        // Create root command with options
+        var rootCommand = new RootCommand("A2AClient");
+        rootCommand.SetHandler(HandleCommandsAsync);
+
+        // Run the command
+        return await rootCommand.InvokeAsync(args);
+    }
+
+    public static async System.Threading.Tasks.Task HandleCommandsAsync(InvocationContext context)
+    {
+        await RunCliAsync();
+    }
+
+    #region private
+    private static async System.Threading.Tasks.Task RunCliAsync()
+    {
+        // Set up the logging
+        using var loggerFactory = LoggerFactory.Create(builder =>
+        {
+            builder.AddConsole();
+            builder.SetMinimumLevel(LogLevel.Information);
+        });
+        var logger = loggerFactory.CreateLogger("A2AClient");
+
+        // Retrieve configuration settings
+        IConfigurationRoot configRoot = new ConfigurationBuilder()
+            .AddEnvironmentVariables()
+            .AddUserSecrets(Assembly.GetExecutingAssembly())
+            .Build();
+        var apiKey = configRoot["A2AClient:ApiKey"] ?? throw new ArgumentException("A2AClient:ApiKey must be provided");
+        var modelId = configRoot["A2AClient:ModelId"] ?? "gpt-4.1";
+        var agentUrls = configRoot["A2AClient:AgentUrls"] ?? "http://localhost:5000/;http://localhost:5001/;http://localhost:5002/";
+
+        // Create the Host agent
+        var hostAgent = new HostClientAgent(logger);
+        await hostAgent.InitializeAgentAsync(modelId, apiKey, agentUrls!.Split(";"));
+        AgentThread thread = new ChatHistoryAgentThread();
+        try
+        {
+            while (true)
+            {
+                // Get user message
+                Console.Write("\nUser (:q or quit to exit): ");
+                string? message = Console.ReadLine();
+                if (string.IsNullOrWhiteSpace(message))
+                {
+                    Console.WriteLine("Request cannot be empty.");
+                    continue;
+                }
+
+                if (message == ":q" || message == "quit")
+                {
+                    break;
+                }
+
+                await foreach (AgentResponseItem<ChatMessageContent> response in hostAgent.Agent!.InvokeAsync(message, thread))
+                {
+                    Console.ForegroundColor = ConsoleColor.Cyan;
+                    Console.WriteLine($"\nAgent: {response.Message.Content}");
+                    Console.ResetColor();
+
+                    thread = response.Thread;
+                }
+            }
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "An error occurred while running the A2AClient");
+            return;
+        }
+    }
+    #endregion
+}

dotnet/samples/Demos/A2AClientServer/A2AClient/README.md

@@ -0,0 +1,26 @@
+
+# A2A Client Sample
+Show how to create an A2A Client with a command line interface which invokes agents using the A2A protocol.
+
+## Run the Sample
+
+To run the sample, follow these steps:
+
+1. Run the A2A client:
+    ```bash
+    cd A2AClient
+    dotnet run
+    ```  
+2. Enter your request e.g. "Show me all invoices for Contoso?"
+
+## Set Secrets with Secret Manager
+
+The agent urls are provided as a ` ` delimited list of strings
+
+```text
+cd dotnet/samples/Demos/A2AClientServer/A2AClient
+
+dotnet user-secrets set "A2AClient:ModelId" "..."
+dotnet user-secrets set "A2AClient":ApiKey" "..."
+dotnet user-secrets set "A2AClient:AgentUrls" "http://localhost:5000/policy;http://localhost:5000/invoice;http://localhost:5000/logistics"
+```

dotnet/samples/Demos/A2AClientServer/A2AServer/A2AServer.csproj

@@ -0,0 +1,24 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <UserSecretsId>5ee045b0-aea3-4f08-8d31-32d1a6f8fed0</UserSecretsId>
+    <NoWarn>$(NoWarn);CS1591;VSTHRD111;CA2007;SKEXP0110</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="SharpA2A.Core" />
+    <PackageReference Include="SharpA2A.AspNetCore" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Agents\A2A\Agents.A2A.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Agents\AzureAI\Agents.AzureAI.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Agents\Core\Agents.Core.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Connectors\Connectors.OpenAI\Connectors.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>