"Your body" is arbitrary

What defines the boundary of a person's body? I expect we agree that bones are part of a human body, while shoes are separate. Several definitions classify those extremes correctly, but give annoying results on edge cases.

We might say that body parts are those which can only be separated by the power of outside tools. But hair can be pulled out, and fingernails picked shorter, by the casual use of hands.

We might say that the body is all that which the nervous system controls. But if you use a tool fluently enough, your brain comes to process it much like any other limb, adding their abilities into its model of the body. Insofar as your muscle movements control the tool, the tool is ultimately commanded by your nervous system. If we stipulate that it's only part of your body if your nervous system controls it reliably, we get other problems: a limb becomes "separate" from your body whenever its nerves fail and outside electricity gets to the muscles.

We might define the body as physically contiguous. Then an adhesive bandage, once you stick it on, becomes part of your body.

We might define the body as a local cluster of cells. If we identified a specific set of cells, the label would go obsolete as your cells die and are replaced. If we cluster them by location, a leather jacket, formed from an animal's skin cells, is part of your body when you wear it. If we only accept the live ones, the outer layer of epidermis is outside the body.

Our intuition is largely consistent, but a precise definition, so far, eludes me.