AddSingleton does not work as expected

[TedyHH]

Describe the bug
When we register tool like AddSingleton(type, instance) and pass a singleton instance, it seems that the instance is being ignored and the library creates a new instance when it needs it.
I tried also AddSingleton using a factory method like this:
services.AddSingleton(toolType, provider => Activator.CreateInstance(toolType, this.m_compositionService));
A breakpoint to Activator.CreateInstance was never hit and the tool just created the instance of the tool.

To Reproduce
Steps to reproduce the behavior:
1.

Expected behavior
A clear and concise description of what you expected to happen.

Logs
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Additional context
We discussed the issue over email. Please feel free to contact me there if you need additional information. Thanks!

[stephentoub]

Can you please share a minimal repro?

[stephentoub]

Oh, I re-read your issue and understand now. The default handling uses ActivatorUtilities.CreateInstance so, as documented, it always creates a new instance for each invocation. The ctor arguments to the tool type can be satisfied from DI, however, as can arguments to the tool method. If you want a singleton, you can directly register the McpServer Instance with the singleton baked in as the target.

[TedyHH]

Ok. I pinged you on the email to get more clarification and speed up the process. Thanks!