List coaching clients

What your assistant is told

List the calling trainer's active client links. Returns the client_handle (opaque ID) you pass on subsequent read tools to operate on each client's data, plus the scopes the link grants. EMPTY list is the normal answer when the trainer has no paired clients yet — surface that to the user (e.g. "You don't have any paired clients yet — they need to pair via Settings → Coaches."). Requires the caller to have toggled Coaching mode on; non-trainers get an empty list, not an error.