I can not use ABI unfortunately because I am trying to use it in Wordpress PHP. It would work there with the nested array. I would like to construct a class from the returned data, but I do not know which is the last argument of that Vec. The only solution I see is to also send the arguments amount before. Or is there a better way you know?

You have a few possibilities. 1. Implement your own abi handling so you know for each endpoint how to correctly decode the data. 2. Don't use the multivaluemanagedvec and instead have a normal managed vec and split that accordingly 3. Make the vec your last value, so you know that first comes the address, then the number and the rest is part of the vec 4. Make a logic to take the first value and the last value and let the rest be the vec.