Refill this key's wallet

Available only to a key issued with purchasing enabled, and only up to what the key may still spend (cap − spent − current balance): a purchase can never lift the key's own spend cap. Raising the cap and enabling purchasing are human actions.

status: charged means the payment provider accepted the collection from a saved payment method — not that the tokens have landed; they are credited when the payment is confirmed, so poll /tokens/balance. status: requires_human means no saved payment method was available: nothing was charged and checkout_url is for a person to open.

A human session is refused here with AGENT_KEY_REQUIRED — the apps have a real checkout with card entry and 3-D Secure.

Named like every other paid call: this is the one endpoint where software starts a charge, so a call that times out after the provider took it comes back as the same purchase rather than a second one.