Credits: the three pools and the order they are spent

What a credit is

A credit is the unit every API call costs. Simple tools cost 1; tools that do real network or compute work cost more. Each tool's page and the API reference state its exact cost, and the cost is charged per successful call.

The three pools

Your workspace can hold credits in three places at once. They spend identically — the difference is where they came from, when they expire, and the order they are used.

1. Monthly allowance

Comes with a subscription. It refreshes at the start of every billing cycle and does not roll over — an unused allowance is gone when the cycle turns. That is what a plan is: a monthly quantity at a monthly price.

2. Carried credits

Created when you change plan mid-cycle. Whatever is left of your old allowance is carried across so that changing plan does not destroy value you already paid for.

Carried credits keep the original expiry date — the date your old plan's cycle would have ended, not your new one's.

3. Purchased credits

Bought as a credit pack. No subscription needed, and they are yours: they last twelve months from purchase and are unaffected by plan changes.

The spend order

carried credits  →  monthly allowance  →  purchased credits

This is not arbitrary. It is soonest-to-expire first. Carried credits die first, so they are spent first; purchased credits last the longest, so they are kept for last.

The effect is that you cannot lose credits to expiry while newer ones are being spent — which is exactly what would happen under the obvious ordering.

Why the balance is shown split

The Top up credits page shows the pools separately, with when each is spent and when each expires. One combined number hid the fact that carried credits are used first, which made a plan change look like it had quietly demoted your credits to the back of the queue.

What happens when credits run out

A call that cannot be paid for is refused with a clear error rather than silently failing or running up a debt. Turn on auto-refill if you would rather top up automatically than be interrupted.