Prompt not visible in Claude Desktop

[RYanamandra-ctm]

Describe the bug
I'm trying to create a prompt, but I don't see it when I test the Stdio server with Desktop Claude. This is similar to #186

To Reproduce
`[McpServerPromptType]
public static class MyPrompts
{
[McpServerPrompt, Description("Creates a prompt to summarize the provided message.")]
public static ChatMessage Summarize([Description("The content to summarize")] string content) =>
new(ChatRole.User, $"Please summarize this content into a single sentence: {content}");

}`

Expected behavior
Be able to see and use the prompt in Claude Desktop.

Logs
If applicable, add logs to help explain your problem.

Additional context

• I'm using the latest nuget package. <PackageReference Include="ModelContextProtocol" Version="0.1.0-preview.12" />

[stephentoub]

Can you share a complete repro? How are you loading in MyPrompts?

[RYanamandra-ctm]

I'm loading it using builder.Services .AddMcpServer() .WithStdioServerTransport() .WithPromptsFromAssembly() .WithToolsFromAssembly();

var builder = Host.CreateApplicationBuilder();

builder.Services
.AddMcpServer()
.WithStdioServerTransport()
.WithPromptsFromAssembly()
.WithToolsFromAssembly();

builder.Services.AddSingleton<ILogger>(sp => sp.GetRequiredService<ILogger<Program>>());

var app = builder.Build();

await app.RunAsync();

[McpServerPromptType]
public static class MyPrompts
{
  [McpServerPrompt, Description("Creates a prompt to summarize the provided message.")]
  public static ChatMessage Summarize([Description("The content to summarize")] string content) =>
    new(ChatRole.User, $"Please summarize this content into a single sentence: {content}");
}

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net9.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
    </PropertyGroup>
    <ItemGroup>
        <PackageReference Include="Microsoft.Extensions.Hosting" Version="10.0.0-preview.3.25171.5" />
        <PackageReference Include="Microsoft.Extensions.Http" Version="9.0.4" />
        <PackageReference Include="ModelContextProtocol" Version="0.1.0-preview.12"/>
    </ItemGroup>
</Project>

[stephentoub]

I've not tried your repro, but just from glancing at it, I expect you're logging to stdout, which is going to interfere with this using a stdio transport. As in the README, try adding:

builder.Logging.AddConsole(consoleLogOptions =>
{
    // Configure all logs to go to stderr
    consoleLogOptions.LogToStandardErrorThreshold = LogLevel.Trace;
});