Remote MCP Server Using .NET SDK: Prompts

This repository contains a sample remote Model Context Protocol (MCP) server built with the .NET SDK and ModelContextProtocol.AspNetCore.

The server exposes:

• MCP tools (for operations such as ping and weather lookup)
• MCP prompts (for reusable instruction templates)
• HTTP MCP endpoint at /mcp
• Health endpoint at /api/healthz

What This Project Is

The project is an ASP.NET Core MCP server that can be used by MCP clients (including VS Code MCP client configuration in .vscode/mcp.json).

Source layout:

• src/McpServer/McpServer: MCP host application
• src/McpServer/WeatherService: weather service used by the weather tool
• scripts: PowerShell scripts to list and call MCP tools/resources/prompts

Prerequisites

• Windows with PowerShell (pwsh or Windows PowerShell)
• .NET SDK 10.0 (project targets net10.0)
• VS Code with MCP client support
• Internet access for weather lookup (uses Open-Meteo APIs)

Run The Server Locally

From the repository root:

dotnet restore .\src\McpServer\McpServer.slnx
dotnet run --project .\src\McpServer\McpServer\McpServer.csproj

Default server URL:

• http://0.0.0.0:8081/mcp

Notes:

• Port is controlled by FUNCTIONS_CUSTOMHANDLER_PORT (defaults to 8081).
• Health check endpoint: http://localhost:8081/api/healthz

VS Code MCP Client Configuration

This repository already includes .vscode/mcp.json:

{
  "servers": {
    "local-mcp-server": {
      "url": "http://0.0.0.0:8081/mcp",
      "type": "http"
    }
  }
}

If needed, update url to match your local port.

Exposed MCP Tools

Defined in src/McpServer/McpServer/McpServerTools.cs:

• Ping(message: string)
  • Verifies server responsiveness and optionally echoes a message.
• GetWeather(city: string)
  • Returns current weather data for the requested city.

Tool names shown by MCP clients can be normalized by the MCP library. Use tools/list (or the script below) to confirm exact callable names in your environment.

Exposed MCP Prompts

Defined in src/McpServer/McpServer/McpServerPrompts.cs and registered in src/McpServer/McpServer/Program.cs with:

.WithPrompts<McpServerPrompts>();

Available prompts:

• default_prompt

  • Description: Default system prompt for the MCP server.
  • Returns a concise system instruction set:
    • be concise
    • prefer plain text
    • do not hallucinate
    • ask for clarification when input is unclear

• weather_query_guide(userContext?: string)

  • Description: Guidance on how to ask for weather forecasts in a structured way.
  • Optional argument:
    • userContext: extra location or preference context appended to the prompt output.

• weather_data_interpretation

  • Description: Instructions for interpreting weather forecast data returned by the server.
  • Includes formatting guidance for temperature, summary, context, and recommendations.

Use prompts/list to see exact prompt names and argument metadata in your runtime.

How To Create A New MCP Prompt

Use this pattern from McpServerPrompts when adding a new prompt.

1. Add or reuse a prompt container class and mark it with [McpServerPromptType].
2. Add a public method and mark it with [McpServerPrompt].
3. Add a [Description("...")] attribute so clients can show meaningful metadata.
4. For input arguments, add [Description("...")] attributes for better client introspection.
5. Return string or Task<string>.
6. Ensure the prompt type is registered in startup (already done with .WithPrompts<McpServerPrompts>()).
7. Run the server and validate with prompts/list and prompts/get.

Example (new prompt in McpServerPrompts.cs):

[McpServerPrompt]
[Description("Provides concise guidance for travel weather planning")]
public Task<string> TravelWeatherGuide(
    [Description("Destination city")] string city,
    [Description("Optional number of travel days")] int? days = null)
{
    var output = $"""
    # Travel Weather Guide

    Destination: {city}
    Duration: {(days.HasValue ? $"{days} day(s)" : "unspecified")}

    Ask for:
    - daily highs/lows
    - rain probability
    - wind conditions
    """;

    return Task.FromResult(output);
}

After adding the method, test it:

# 1) Start server
dotnet run --project .\src\McpServer\McpServer\McpServer.csproj

# 2) List prompts and confirm the new prompt name
.\scripts\list-mcp-server-prompts.ps1

# 3) Get the prompt by name
.\scripts\call-mcp-prompt.ps1 -PromptName "travel_weather_guide"

Scripts

Scripts are in scripts/:

• scripts/list-mcp-server-tools.ps1
  • Calls MCP tools/list and prints discovered tools and schemas.
• scripts/call-mcp-tool.ps1
  • Calls MCP tools/call for a specific tool and arguments.
  • Defaults: toolName=get_weather, toolParams=@{ city = "Paris" }.
• scripts/list-mcp-server-prompts.ps1
  • Calls MCP prompts/list and prints discovered prompts and arguments.
• scripts/call-mcp-prompt.ps1
  • Calls MCP prompts/get for a specific prompt name.
  • Default prompt name: weather_query_guide.

Optional resource scripts are also present if you still want to inspect MCP resources:

• scripts/list-mcp-server-resources.ps1
• scripts/call-mcp-resources.ps1

Quick Test Examples

Run these from the repository root in a second terminal while the server is running.

Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force;

List available tools:

.\scripts\list-mcp-server-tools.ps1

Call ping tool:

.\scripts\call-mcp-tool.ps1 -toolName "ping" -toolParams @{ message = "hello from local test" }

Call weather tool:

.\scripts\call-mcp-tool.ps1 -toolName "get_weather" -toolParams @{ city = "Paris" }

List available prompts:

.\scripts\list-mcp-server-prompts.ps1

Get default prompt:

.\scripts\call-mcp-prompt.ps1 -PromptName "default_prompt"

Get weather query guide prompt:

.\scripts\call-mcp-prompt.ps1 -PromptName "weather_query_guide"

Get weather interpretation prompt:

.\scripts\call-mcp-prompt.ps1 -PromptName "weather_data_interpretation"