mcp usage sample (#490)

* mcp usage sample

* simplified dependencies of ToMessage

* cleaned up usings

Author: KrzysztofCwalina

docs/guides/mcp/chat_with_mcp.cs

@@ -0,0 +1,89 @@
+// SAMPLE: call the official MCP library for .NET
+
+#:package OpenAI@2.2.*-*
+#:package ModelContextProtocol.Core@*-*
+#:property PublishAot=false
+
+using ModelContextProtocol;
+using ModelContextProtocol.Client;
+using OpenAI.Chat;
+
+string mcpCommand = Environment.GetEnvironmentVariable("MCP_SERVER_COMMAND")!; // path to a stdio mcp server
+string key = Environment.GetEnvironmentVariable("OPENAI_KEY")!;
+
+ChatClient chatClient = new("gpt-4.1", key);
+
+// Create MCP client to connect to the server
+IMcpClient mcpClient = await McpClientFactory.CreateAsync(new StdioClientTransport(new StdioClientTransportOptions
+{
+    Name = "MyServer",
+    Command = mcpCommand,
+    Arguments = [],
+}));
+
+// get avaliable tools and add them to completion options
+ChatCompletionOptions options = new();
+await foreach (McpClientTool chatTool in mcpClient.EnumerateToolsAsync())
+{
+    options.Tools.Add(chatTool.AsOpenAIChatTool());
+}
+
+// conversation thread
+List<ChatMessage> conversation = new()
+{
+    ChatMessage.CreateUserMessage("Use an MCP tool")
+};
+
+start:
+ChatCompletion chatCompletion = chatClient.CompleteChat(conversation, options);
+conversation.Add(ChatMessage.CreateAssistantMessage(chatCompletion));
+switch (chatCompletion.FinishReason)
+{
+    case ChatFinishReason.ToolCalls:
+        foreach(var call in chatCompletion.ToolCalls)
+        {
+            var mcpArguments = call.FunctionArguments.ToObjectFromJson<Dictionary<string, object>>();
+            Console.WriteLine("Tool call detected, calling MCP server...");
+            ModelContextProtocol.Protocol.CallToolResult result = await mcpClient.CallToolAsync(call.FunctionName, mcpArguments!);
+            Console.WriteLine($"tool call result {result.Content[0]}");
+            ChatMessage message = call.ToMessage(result.Content.ToAIContents());
+            conversation.Add(message);
+        }     
+        goto start;
+    case ChatFinishReason.Stop:
+        Console.WriteLine(chatCompletion.Content[0].Text);
+        break;
+    default:
+        throw new NotImplementedException();
+}
+
+#region TEMPORARY
+// this is temporary. all these APIs will endup being in one of the packages used here. 
+public static class TemporaryExtensions
+{
+    // this needs to be in the adapter package
+    public static ChatMessage ToMessage(this ChatToolCall openaiCall, IEnumerable<Microsoft.Extensions.AI.AIContent> contents)
+    {
+        List<ChatMessageContentPart> parts = new();
+        foreach (Microsoft.Extensions.AI.AIContent content in contents)
+        {
+            string serialized = System.Text.Json.JsonSerializer.Serialize(content.RawRepresentation);
+            using System.Text.Json.JsonDocument json = System.Text.Json.JsonDocument.Parse(serialized);
+            System.Text.Json.JsonElement text = json.RootElement.GetProperty("text");
+            string textValue = text.GetString() ?? string.Empty;
+            parts.Add(ChatMessageContentPart.CreateTextPart(textValue));
+        }
+        ToolChatMessage message = ChatMessage.CreateToolMessage(openaiCall.Id, parts);
+        return message;
+    }
+
+    // this is in the adapter package
+    public static ChatTool AsOpenAIChatTool(this Microsoft.Extensions.AI.AIFunction mcpTool)
+    {
+        return ChatTool.CreateFunctionTool(
+            mcpTool.Name,
+            mcpTool.Description,
+            BinaryData.FromString(mcpTool.JsonSchema.GetRawText()));
+    }
+}
+#endregion