Expose metadata from A2AAgent and seal AIAgentMetadata (#3417)

dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs

@@ -26,6 +26,8 @@ namespace Microsoft.Agents.AI.A2A;
 /// </remarks>
 public sealed class A2AAgent : AIAgent
 {
+    private static readonly AIAgentMetadata s_agentMetadata = new("a2a");
+
     private readonly A2AClient _a2aClient;
     private readonly string? _id;
     private readonly string? _name;
@@ -211,6 +213,13 @@ public sealed class A2AAgent : AIAgent
     /// <inheritdoc/>
     public override string? Description => this._description;
 
+    /// <inheritdoc/>
+    public override object? GetService(Type serviceType, object? serviceKey = null)
+        => base.GetService(serviceType, serviceKey)
+           ?? (serviceType == typeof(A2AClient) ? this._a2aClient
+            : serviceType == typeof(AIAgentMetadata) ? s_agentMetadata
+            : null);
+
     private async ValueTask<A2AAgentSession> GetA2ASessionAsync(AgentSession? session, AgentRunOptions? options, CancellationToken cancellationToken)
     {
         // Aligning with other agent implementations that support background responses, where

dotnet/src/Microsoft.Agents.AI.Abstractions/AIAgentMetadata.cs

@@ -12,7 +12,7 @@ namespace Microsoft.Agents.AI;
 /// telemetry, and logging purposes.
 /// </remarks>
 [DebuggerDisplay("ProviderName = {ProviderName}")]
-public class AIAgentMetadata
+public sealed class AIAgentMetadata
 {
     /// <summary>
     /// Initializes a new instance of the <see cref="AIAgentMetadata"/> class.

dotnet/tests/Microsoft.Agents.AI.A2A.UnitTests/A2AAgentTests.cs

@@ -1027,6 +1027,127 @@ public sealed class A2AAgentTests : IDisposable
         await Assert.ThrowsAsync<InvalidOperationException>(async () => await this._agent.RunStreamingAsync(inputMessages, invalidSession).ToListAsync());
     }
 
+    #region GetService Method Tests
+
+    /// <summary>
+    /// Verify that GetService returns A2AClient when requested.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingA2AClient_ReturnsA2AClient()
+    {
+        // Arrange & Act
+        var result = this._agent.GetService(typeof(A2AClient));
+
+        // Assert
+        Assert.NotNull(result);
+        Assert.Same(this._a2aClient, result);
+    }
+
+    /// <summary>
+    /// Verify that GetService returns AIAgentMetadata when requested.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingAIAgentMetadata_ReturnsMetadata()
+    {
+        // Arrange & Act
+        var result = this._agent.GetService(typeof(AIAgentMetadata));
+
+        // Assert
+        Assert.NotNull(result);
+        Assert.IsType<AIAgentMetadata>(result);
+        var metadata = (AIAgentMetadata)result;
+        Assert.Equal("a2a", metadata.ProviderName);
+    }
+
+    /// <summary>
+    /// Verify that GetService returns null for unknown service types.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingUnknownServiceType_ReturnsNull()
+    {
+        // Arrange & Act
+        var result = this._agent.GetService(typeof(string));
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    /// <summary>
+    /// Verify that GetService with serviceKey parameter returns null for unknown service types.
+    /// </summary>
+    [Fact]
+    public void GetService_WithServiceKey_ReturnsNull()
+    {
+        // Arrange & Act
+        var result = this._agent.GetService(typeof(string), "test-key");
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    /// <summary>
+    /// Verify that GetService calls base.GetService() first and returns the agent itself when requesting A2AAgent type.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingA2AAgentType_ReturnsBaseImplementation()
+    {
+        // Arrange & Act
+        var result = this._agent.GetService(typeof(A2AAgent));
+
+        // Assert
+        Assert.NotNull(result);
+        Assert.Same(this._agent, result);
+    }
+
+    /// <summary>
+    /// Verify that GetService calls base.GetService() first and returns the agent itself when requesting AIAgent type.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingAIAgentType_ReturnsBaseImplementation()
+    {
+        // Arrange & Act
+        var result = this._agent.GetService(typeof(AIAgent));
+
+        // Assert
+        Assert.NotNull(result);
+        Assert.Same(this._agent, result);
+    }
+
+    /// <summary>
+    /// Verify that GetService calls base.GetService() first but continues to derived logic when base returns null.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingA2AClientWithServiceKey_CallsBaseFirstThenDerivedLogic()
+    {
+        // Arrange & Act - Request A2AClient with a service key (base.GetService will return null due to serviceKey)
+        var result = this._agent.GetService(typeof(A2AClient), "some-key");
+
+        // Assert
+        Assert.NotNull(result);
+        Assert.Same(this._a2aClient, result);
+    }
+
+    /// <summary>
+    /// Verify that GetService returns consistent AIAgentMetadata across multiple calls.
+    /// </summary>
+    [Fact]
+    public void GetService_RequestingAIAgentMetadata_ReturnsConsistentMetadata()
+    {
+        // Arrange & Act
+        var result1 = this._agent.GetService(typeof(AIAgentMetadata));
+        var result2 = this._agent.GetService(typeof(AIAgentMetadata));
+
+        // Assert
+        Assert.NotNull(result1);
+        Assert.NotNull(result2);
+        Assert.Same(result1, result2); // Should return the same instance
+        Assert.IsType<AIAgentMetadata>(result1);
+        var metadata = (AIAgentMetadata)result1;
+        Assert.Equal("a2a", metadata.ProviderName);
+    }
+
+    #endregion
+
     public void Dispose()
     {
         this._handler.Dispose();