What you are actually paying for
An agent's daily cost splits into three buckets. Most cost guides blur them together; separating them is how you control the bill:
- Model inference. The tokens the agent burns thinking and answering. This is usually the biggest slice and it lives with your model provider, priced per token.
- Tool and API access. The capabilities the agent calls: data lookups, verifications, actions. This is the slice you can shop for, and the one this page prices.
- Your oversight time. Reviewing what the agent did. This cost drops to near zero when every action carries a verifiable receipt you can check in seconds instead of re-running the work.
We will not invent prices for anyone else's slice. For the tool-access slice, here are Zambo's verified numbers: a free tier with daily limits, a $0.99 Day Pass for 24 hours of higher limits, and a $29/month pass for heavy use. Everything below is built on those.
The three pricing models, compared
Per-call metering. You pay for each tool call. Fair in theory, unpredictable in practice: an agent in a loop can make hundreds of calls before you notice. Good for rare, high-value calls. Bad for anything autonomous. And when you do stop a runaway agent, the stop itself needs proof: kill switch proof covers the receipts that show an agent actually stopped.
Monthly subscription. Flat rate, predictable, but you pay for idle days. Good when the agent works every day. At $29/month, you are paying roughly $0.97 per day whether the agent works or not.
Day pass. Flat rate for 24 hours, bought only on days you use it. At $0.99 per active day, the math is blunt: if you need full access fewer than 29 days a month, day passes beat the $29 subscription ($29 / $0.99 is about 29.3). If the agent runs daily, subscribe.
The break-even rule
Count your active days per month. Fewer than 29: buy day passes at zambo.dev/day-pass. Every day: take the $29/month pass. Agents, which work in bursts, almost always land on the day-pass side.
Spending-limit patterns that actually work
The fear with agents is not the price per call. It is the runaway loop. Four patterns keep it contained:
- Daily call caps. The free tier enforces them by default. Know your cap before you hand an agent the keys.
- Time-boxed access. A 24-hour pass is a natural circuit breaker: even a misbehaving agent stops costing you tomorrow.
- Per-tool limits. The expensive or sensitive tools keep their own limits, separate from the general pool.
- Receipt-level auditing. Every Zambo tool call returns a verifiable execution receipt at zambo.dev/run/<id>. When the bill surprises you, the receipts show exactly which calls caused it. An audit trail beats a spending alert.
The last pattern is the underrated one. Most agent bills are mysteries: a total with no itemization. Receipts itemize every call by construction. You do not guess where the money went; you read it.
Where Zambo fits in your agent budget
Start free and watch the receipts pile up. When you hit the daily limits on a day that matters, the Day Pass is $0.99, bought by you in PayPal or by the agent itself in USDC on Base through the x402 flow. When every day matters, $29/month. No per-call metering on the pass, no idle-day waste on the day pass, no surprise line items anywhere: the receipts are the invoice.
Try the math on your own workload
Run your agent on the free tier for a day. Count the receipts. Multiply your active days by $0.99. That number is your honest monthly cost, and you computed it from evidence instead of a pricing page.