Temperament first, size second
The pony that keeps a child safe is the one whose reactions are slow, predictable and forgiving, and those qualities have very little to do with height. A pony standing a hand taller than you pictured, who has carried children for years and thinks before he spooks, will usually do a better job than a dainty pony who is quick, strong-willed and sharp off the leg. Ask what the pony does when something goes wrong: the one who plants his feet and looks is a safer teacher than the one who spins and runs, whatever their sizes. Age is part of the picture too — a pony in his teens who has been there and done it has a steadiness that a five-year-old, however sweet, has not yet grown into.
Watch the pony live its ordinary day
Do not judge a pony on a ridden display alone. Ask to see it caught in the field, because a pony that cannot be caught will sour every ride before it starts. Watch it groomed, its feet picked up, and its tack put on, and note whether it fidgets, threatens or simply stands. See it ridden in an arena and out on a hack, past traffic, dogs and flapping things, ideally by a child of similar size to yours. Ponies are often quietest inside their own routine, so what you see on an ordinary afternoon tells you more than a polished performance arranged for visitors. If you can, watch it turned out with other ponies too — a pony that bullies or is bullied in the field shows you a side of its temperament the stable hides.
More than one visit, and a vet's eyes
Visit at least twice, at different times of day, and if the seller agrees, ask about a short trial at your own yard, where the pony's behaviour without its usual companions is the real test. Whatever its history, have it examined by a vet before you buy: eyes, heart, teeth and soundness checked properly, because a charming pony with a hidden problem helps nobody. Ask the seller plainly why the pony is for sale, how long they have had it, and what it is like to clip, load and have its feet done. A seller who knows the pony well and answers without hurry is a good sign in itself.
The history that should travel with the pony
A first pony's past is working information, not paperwork for its own sake: what it eats, when its teeth were last done, any past illness or lameness, and the quirks the current owner manages without thinking — head-shy on one side, happier living out, restless without a companion in sight. That history protects the child as much as the pony, because most early problems in a new home come from unknowingly changing something that mattered. This is where KinsLe's Transferrable Profiles earn their place: the pony's profile moves to you with its records, routines and known quirks intact, so the pony your child rides on day one is the same pony, on paper, that the seller described.