QuickstartClient

MCP Client Quickstart with MCP C# SDK

System Requirements

Before starting, ensure your system meets these requirements:

• .NET 8.0 or higher
• Anthropic API key (Claude)
• Windows, Linux, or MacOS

Setting up your environment

First, create a new .NET project:

dotnet new console -n QuickstartClient
cd QuickstartClient

Then, add the required dependencies to your project:

dotnet add package ModelContextProtocol --prerelease
dotnet add package Anthropic.SDK
dotnet add package Microsoft.Extensions.Hosting

Setting up your API key

You'll need an Anthropic API key from the Anthropic Console.

dotnet user-secrets init
dotnet user-secrets set "ANTHROPIC_API_KEY" "<your key here>"

Creating the Client

Basic Client Structure

First, let's setup the basic client class:

using Anthropic.SDK;
using Microsoft.Extensions.AI;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol.Transport;

var builder = Host.CreateApplicationBuilder(args);

builder.Configuration
    .AddEnvironmentVariables()
    .AddUserSecrets<Program>();

This creates the beginnings of a .NET console application that can read the API key from user secrets.

Next, we'll setup the MCP Client:

var (command, arguments) = GetCommandAndArguments(args);

var clientTransport = new StdioClientTransport(new()
{
    Name = "Demo Server",
    Command = command,
    Arguments = arguments,
});

await using var mcpClient = await McpClientFactory.CreateAsync(clientTransport);

var tools = await mcpClient.ListToolsAsync();
foreach (var tool in tools)
{
    Console.WriteLine($"Connected to server with tools: {tool.Name}");
}

Add this function at the end of the Program.cs file:

static (string command, string[] arguments) GetCommandAndArguments(string[] args)
{
    return args switch
    {
        [var script] when script.EndsWith(".py") => ("python", args),
        [var script] when script.EndsWith(".js") => ("node", args),
        [var script] when Directory.Exists(script) || (File.Exists(script) && script.EndsWith(".csproj")) => ("dotnet", ["run", "--project", script, "--no-build"]),
        _ => throw new NotSupportedException("An unsupported server script was provided. Supported scripts are .py, .js, or .csproj")
    };
}

This creates and configures a MCP client that will connect to a server that is provided as a command line argument. It then lists the available tools from the connected server.

Query processing logic

Now let's add the core functionality for processing queries and handling tool calls:

using var anthropicClient = new AnthropicClient(new APIAuthentication(builder.Configuration["ANTHROPIC_API_KEY"]))
    .Messages
    .AsBuilder()
    .UseFunctionInvocation()
    .Build();

var options = new ChatOptions
{
    MaxOutputTokens = 1000,
    ModelId = "claude-3-5-sonnet-20241022",
    Tools = [.. tools]
};

Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("MCP Client Started!");
Console.ResetColor();

PromptForInput();
while(Console.ReadLine() is string query && !"exit".Equals(query, StringComparison.OrdinalIgnoreCase))
{
    if (string.IsNullOrWhiteSpace(query))
    {
        PromptForInput();
        continue;
    }

    await foreach (var message in anthropicClient.GetStreamingResponseAsync(query, options))
    {
        Console.Write(message);
    }
    Console.WriteLine();

    PromptForInput();
}

static void PromptForInput()
{
    Console.WriteLine("Enter a command (or 'exit' to quit):");
    Console.ForegroundColor = ConsoleColor.Cyan;
    Console.Write("> ");
    Console.ResetColor();
}

Key Components Explained

1. Client Initialization

• The client is initialized using McpClientFactory.CreateAsync(), which sets up the transport type and command to run the server.

2. Server Connection

• Supports Python, Node.js, and .NET servers.
• The server is started using the command specified in the arguments.
• Configures to use stdio for communication with the server.
• Initializes the session and available tools.

3. Query Processing

• Leverages Microsoft.Extensions.AI for the chat client.
• Configures the IChatClient to use automatic tool (function) invocation.
• The client reads user input and sends it to the server.
• The server processes the query and returns a response.
• The response is displayed to the user.

Running the Client

To run your client with any MCP server:

dotnet run -- path/to/server.csproj # dotnet server
dotnet run -- path/to/server.py # python server
dotnet run -- path/to/server.js # node server

The client will:

1. Connect to the specified server
2. List available tools
3. Start an interactive chat session where you can:
   • Enter queries
   • See tool executions
   • Get responses from Claude
4. Exit the session when done

Here's an example of what it should look like it connected to a weather server quickstart: