Would be nice if the doco at https://n8n.io/workflows/8 included the parameters etc so this could be used as a reference when people wish to write their own custom error handler.
I know read code is also a valid answer but in the spirit of completeness it should be here.
Welcome to the community @mP1!
That page is less for documentation more for reference and to show some examples. If you want to know the available parameters there are multiple ways:
I hope that helps. If not simply get back to me.
Think “read the code” could be a valid answer for some projects but as we aim to be usable by everybody also non-programmers (sadly not 100% there yet) would it not be one for us.