IMcpServerBuilder WithTools cannot pass parameters to tool constructor

[asklar]

Describe the bug
I'd expect to be able to write something like:

serverBuilder.WithTools((sb) => { new MyTool(42); });

To Reproduce
serverBuilder.WithTools(42); // doesn't compile

Expected behavior
I can pass a lambda or vararg style params through to the tool's ctor

Logs
n/a

[stephentoub]

What is it you're trying to accomplish? I'm not understanding the code sample.

[asklar]

I want to have:

[McpServerToolType]
public class MyTool
{
    public MyTool(int x) { this.x = x; }
    private int x;

    [McpServerTool, Description("...")]
    public string DoSomething() { /* use x */ }
}

then in my program, I need to be able to pass 42 to the MyTool ctor, e.g.

var builder = Host.CreateApplicationBuilder();
var serverBuilder = builder.Services.AddMcpServer()
    .WithStdioServerTransport();
    .WithTools<MyTool>(42);
// ...

However, I cannot pass params to the WithTools method.

[stephentoub]

Today you can do:

.WithTools([McpServerTool.Create(new MyTool(42).DoSomething)])

or if you wanted to control which methods were used:

MyTool tool = new(42);
...
    .WithTools(from m in typeof(MyTool).GetMethods()
               where m.GetCustomAttribute<McpServerToolAttribute>() is not null 
               select McpServerTool.Create(m, tool))

or if you wanted to use constructor parameters sourced from the dependency injection container, that "just works", e.g.

[McpServerToolType]
public class MyTool(HttpClient client) // this will come from DI
{
    ...
}

Are you asking for another overload of WithTool<TToolType>() that accepts a TToolType instance?

[asklar]

Thanks Stephen. Yes, either:
.WithTools<TTool>(TTool tool);

or
.WithTools<TTool>(Func<TTool> action);

[asklar]

thanks all!