class PluginManager:
    def __init__(self):
        self.tools = {}

    def register(self, name, func):
        if not callable(func):
            raise ValueError(f"Plugin '{name}' is not callable.")
        self.tools[name] = func

    def list_plugins(self):
        return list(self.tools.keys())

    def call(self, name, *args, **kwargs):
        if name not in self.tools:
            return f"[PluginManager] Tool '{name}' not found."
        try:
            return self.tools[name](*args, **kwargs)
        except Exception as e:
            return f"[PluginManager Error] {str(e)}"