The boundaries that trace to a document
A distinct set of limits is written down. The standard contract terms address deploying a helper to a second household, to a family business, or to tasks such as washing the family car, and these are best treated as fixed because they rest on an explicit rule rather than opinion.
For these, the answer to "is this allowed?" is a matter of reading the term, not weighing a situation. The detailed duty-boundary guides set out each one and its source.
The boundaries that do not
Other limits have no equivalent document. Where basic, non-clinical home support ends and skilled medical care begins is not divided task-by-task in any statute — the relevant professional and poisons legislation does not set a home-care checklist. That makes it a judgment about safety and competence, not a rule to look up.
The safe approach mirrors the guides: keep clinical decisions with a qualified clinician, match any care task to demonstrated training, and add a safety caveat rather than relying on a legal technicality. Flattening this into "everything traces to a rule" is the mistake to avoid.