The withTool, withResource, withResourceTemplate, withPrompt, etc. all expect a callback as their first parameter but cannot handle native php callbacks (e.g. fn () => $foo()). This oversights makes adding dynamic callbacks very hard/impossible.

Is there anything that prevents from opening up for callables in general?

Edit: basically the same for registerTool, registerResource, registerResourceTemplate, registerPrompt, ..., which expect both a class & method name.