>Ah, interesting, didn't know that about builtins. Perhaps there should be a method to manually specify this? To avoid the situation where calling the function has undesirable side-effects. Or is it enough to just assume n_args is 1 for builtins?

I'm not sure we would want to assume `n_args=1`.  It would be weird, but not inconceivable, for someone to do something like 
```python
nengo.Node(output=max)
```
(I don't know man, people do crazy things).  The try-except thing is ugly, but it's actually not too bad in this case, because you only need to check 0 and 1, and otherwise assume >=2.