Sand can be a useful component in a garden soil mix, but it is not always necessary or desirable. The addition of sand can improve drainage and aeration in heavy, clay soils, but if the soil is already well-draining, adding sand can create problems by increasing the soil's alkalinity and reducing its ability to hold moisture and nutrients.

You should be able to grab a handful, squeeze it and it should be able hold its shape. If it crumbles too easily then there is too much sand. If it does not crumble at all then sand would be a favorable addition.