Addressed initial PR comments.

dotnet/samples/03-workflows/Declarative/InvokeFoundryToolboxMcp/InvokeFoundryToolboxMcp.yaml

@@ -37,7 +37,7 @@ trigger:
       toolName: tools/list
       conversationId: =System.ConversationId
       headers:
-       Foundry-Features: Toolboxes=V1Preview
+        Foundry-Features: Toolboxes=V1Preview
       output:
         autoSend: true
         result: Local.ToolboxTools
@@ -50,7 +50,7 @@ trigger:
       toolName: =Env.FOUNDRY_TOOLBOX_DOCS_SERVER_LABEL & "___microsoft_docs_search"
       conversationId: =System.ConversationId
       headers:
-       Foundry-Features: Toolboxes=V1Preview
+        Foundry-Features: Toolboxes=V1Preview
       arguments:
         query: =Local.SearchQuery
       output:
@@ -67,7 +67,7 @@ trigger:
       toolName: =Env.FOUNDRY_TOOLBOX_WEB_SEARCH_TOOL_NAME
       conversationId: =System.ConversationId
       headers:
-       Foundry-Features: Toolboxes=V1Preview
+        Foundry-Features: Toolboxes=V1Preview
       arguments:
         search_query: =Local.SearchQuery
       output:

dotnet/samples/03-workflows/Declarative/InvokeFoundryToolboxMcp/Program.cs

@@ -6,6 +6,7 @@
 
 using System.ClientModel;
 using System.ClientModel.Primitives;
+using System.Collections.Concurrent;
 using System.Net.Http.Headers;
 using Azure.AI.Projects;
 using Azure.AI.Projects.Agents;
@@ -60,11 +61,15 @@ internal sealed class Program
         // Ensure sample toolbox and agent exist in Foundry
         string toolboxEndpoint = await CreateSampleToolboxAsync(toolboxName, docsServerLabel, foundryEndpoint, credential);
         string toolboxMcpServerUrl = BuildToolboxMcpServerUrl(toolboxEndpoint, toolboxName, toolboxApiVersion);
-        Environment.SetEnvironmentVariable(ToolboxMcpServerUrlSetting, toolboxMcpServerUrl);
-        // Expose the server label to the workflow so the YAML can build prefixed MCP tool names dynamically.
-        Environment.SetEnvironmentVariable(DocsServerLabelSetting, docsServerLabel);
-        // Expose the web search tool name so the YAML can reference it without hard-coding.
-        Environment.SetEnvironmentVariable(WebSearchToolNameSetting, webSearchToolName);
+        IConfiguration workflowConfiguration = new ConfigurationBuilder()
+            .AddConfiguration(configuration)
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                [ToolboxMcpServerUrlSetting] = toolboxMcpServerUrl,
+                [DocsServerLabelSetting] = docsServerLabel,
+                [WebSearchToolNameSetting] = webSearchToolName,
+            })
+            .Build();
 
         await CreateAgentAsync(foundryEndpoint, configuration, credential);
 
@@ -72,7 +77,7 @@ internal sealed class Program
         string workflowInput = Application.GetInput(args);
 
         // Create the MCP tool handler for invoking the Foundry toolbox MCP proxy.
-        List<HttpClient> createdHttpClients = [];
+        ConcurrentBag<HttpClient> createdHttpClients = [];
         DefaultMcpToolHandler mcpToolHandler = new(
             httpClientProvider: async (serverUrl, _) =>
             {
@@ -97,6 +102,7 @@ internal sealed class Program
             // Create the workflow factory with MCP tool provider
             WorkflowFactory workflowFactory = new("InvokeFoundryToolboxMcp.yaml", foundryEndpoint)
             {
+                Configuration = workflowConfiguration,
                 McpToolHandler = mcpToolHandler
             };
 

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative.Mcp/DefaultMcpToolHandler.cs

@@ -67,16 +67,13 @@ public sealed class DefaultMcpToolHandler : IMcpToolHandler, IAsyncDisposable
         if (IsListToolsToolName(toolName))
         {
             ThrowIfListToolsArgumentsSpecified(arguments);
+            McpClient listToolsClient = await this.GetOrCreateClientAsync(serverUrl, serverLabel, headers, cancellationToken).ConfigureAwait(false);
+            IList<McpClientTool> tools = await listToolsClient.ListToolsAsync(cancellationToken: cancellationToken).ConfigureAwait(false);
+            return CreateListToolsResultContent(tools.Select(tool => tool.ProtocolTool));
         }
 
         McpClient client = await this.GetOrCreateClientAsync(serverUrl, serverLabel, headers, cancellationToken).ConfigureAwait(false);
 
-        if (IsListToolsToolName(toolName))
-        {
-            IList<McpClientTool> tools = await client.ListToolsAsync(cancellationToken: cancellationToken).ConfigureAwait(false);
-            return CreateListToolsResultContent(tools.Select(tool => tool.ProtocolTool));
-        }
-
         McpServerToolResultContent resultContent = new(Guid.NewGuid().ToString());
 
         // Convert IDictionary to IReadOnlyDictionary for CallToolAsync
@@ -349,6 +346,6 @@ public sealed class DefaultMcpToolHandler : IMcpToolHandler, IAsyncDisposable
             writer.WriteEndObject();
         }
 
-        return Encoding.UTF8.GetString(stream.ToArray());
+        return Encoding.UTF8.GetString(stream.GetBuffer(), 0, (int)stream.Length);
     }
 }