Pay-per-call vs subscription choosing a pricing model for your API.
Subscriptions, prepaid credits, and x402 pay-per-call each fit a different buyer. If your API serves both human developers and AI agents, the answer is usually a split — not a winner.
Pricing model debates usually assume one kind of customer. APIs in 2026 have two: human developers who plan usage in advance, and AI agents that discover a tool mid-task, need it for thirty calls, and may never return.
Those two buyers want opposite things from your pricing. This guide walks through what subscriptions, prepaid credits, and per-call payments each optimize for, and how to run more than one without cannibalizing yourself.
What subscriptions optimize for
A monthly plan gives you predictable revenue and gives a committed customer a predictable bill. For a developer shipping a production feature on top of your API, that trade is fine — they know roughly what they'll consume and they value not thinking about it.
The hidden cost is the front of the funnel. A subscription demands a signup, a card, and a usage forecast before the first useful response. Every prospective customer who just wanted to evaluate your API gets stopped at that gate, and most don't come back.
Prepaid credits: the halfway house
Credits decouple payment from a billing cycle: buy a balance, draw it down per request. That fixes the forecast problem — nobody has to guess their monthly volume — and it caps the customer's exposure.
But credits keep the worst part of subscriptions, the account. Someone still has to register, top up, and manage a balance per provider. A team using fifteen APIs maintains fifteen credit balances, and an autonomous agent can't open an account at all without a human stepping in.
Where both models break: the agent customer
An agent that discovers your API mid-task has no card, no email, and no patience for onboarding. It has a wallet and a budget. If paying you requires anything beyond an HTTP exchange, the agent routes around you to a tool it can pay programmatically.
Agent traffic is also spiky in a way plans punish. A research agent might make 400 calls today and zero for a month. No subscription tier fits that shape — it's either overpaying or hitting a cap mid-task.
What x402 pay-per-call gives you
With x402, your endpoint answers an unpaid request with HTTP 402 and a price. The agent signs a USDC payment, settlement lands on Base in about two seconds, and your handler runs only after payment clears. No signup, no key issuance, no invoice — and no chargebacks, since settled is final.
Per-call pricing starts at $0.01, which is the floor on Loomal. Each response carries an Ed25519-signed receipt, so both sides can prove exactly what was bought. For the long tail of one-off and bursty callers, this converts traffic that subscriptions silently turn away.
Run a split, not a switch
You don't have to migrate anyone. Keep subscriptions for the customers who want commitment pricing — they're real and they're profitable. Add an x402 path for everyone else: agents, evaluators, and bursty workloads that would never sign up.
Set the per-call price above the effective per-call rate of your plans so heavy users still graduate to a subscription. The per-call lane becomes your top of funnel and your agent channel; the plan stays your retention product. List the x402 endpoint on Loomal so agents can discover the price and pay without ever reading your pricing page.
FAQ
Will pay-per-call cannibalize my subscription revenue?
Only if you price it below your plans' effective per-call rate. Set it 2–5x higher and the economics push sustained users toward subscribing, while one-off and agent traffic — which was never going to subscribe — finally pays you something instead of nothing.
Why can't agents just use a metered subscription with an API key?
Someone has to create the account, accept terms, and attach a card — none of which an autonomous agent can do mid-task. x402 collapses authentication and payment into one HTTP exchange: the agent pays per call from its wallet and your handler runs after settlement, with no key to issue or leak.
What does per-call billing cost me in fees?
Payments settle as USDC on Base, and on Loomal the platform fee is 5% of settled transactions, currently waived. Because settlement is on-chain and final in about two seconds, there's no chargeback risk priced into the model.
What's a sensible starting per-call price?
Take your marginal cost per call (compute plus any upstream API fees), multiply by 2–5x, and never go below $0.01, which is the minimum on Loomal. Per-call prices are easy to change, so treat the first number as a hypothesis and adjust against real volume.
Add a pay-per-call lane.
Price your API per call and let agents pay over x402.