```python
def best_harvest(yields: list) -> int:
    if not isinstance(yields, list):
        raise ValueError("Input must be a list.")
    
    total = 0
    for i in range(len(yields)):
        if not isinstance(yields[i], int) or yields[i] < 0:
            raise ValueError("Yield must be an integer and non-negative.")
        
        total += yields[i]
    
    return total
```