These are a commercial slow release fertilizer called Osmocote described as
Each granule is coated with a unique resin that controls nutritional release so that plants get what they need, when they need it.
It is widely used in the greenhouse and nursery industry. If you pick up one of the little beads most of them should be empty and you can easily crush it.
Osmocote fertilizer and the resin shell is not considered harmful and can be left in the pot.