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HTTP 402 does not decide whether a service is free or paid. It is the point where a server tells a client what payment it wants before it returns a protected response. Whether a call is free, metered, or charged per request depends on each provider’s rules. On ArcRouter, the free tier covers free models only, limited to 20 requests per hour per IP, and paid calls cost $0.001 to $0.015 per request depending on complexity. On Arcloak, paid calls are authorized against a payment ceiling and charged for the tokens actually delivered. In both cases, an agent pays only when its wallet and payment policy allow it to sign a payment.
What happens when an agent gets HTTP 402
In the x402 pattern, the 402 response is a machine-readable price quote. The client does not have to guess what to pay or where to send it. A typical exchange runs in five steps:
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- The agent sends an ordinary request to a protected API or model endpoint, with no payment attached.
- The server replies
402 Payment Requiredand includes payment terms. These usually name the accepted network, the asset (for example USDC), the amount, the destination address, and a timeout or payment scheme. - The agent’s payment client compares those terms with its wallet configuration and spending policy. If the terms fall outside the policy, the client refuses to sign.
- If the terms fit, the client signs or authorizes a payment and repeats the original request with the payment payload in a header.
- The service, or a facilitator acting for it, verifies the payment, runs the job, and settles the charge under that implementation’s rules. A successful flow returns the protected response.
Two things follow from this. First, the 402 step is where price is discovered, not where it is set; the provider sets the terms and the agent decides whether to accept them. Second, a 402 challenge tells you what a service wants to be paid. It does not prove the service is trustworthy, returns good output, or is worth the price. Check the provider’s documentation and its data handling before you let an agent spend against it.
Why 402 is not a free-tier standard
There is no shared rule that says a 402-protected endpoint must offer a free allowance, a subscription, or a fixed price. One provider may gate every call behind payment. Another may serve a free model tier on the same platform and only challenge requests that go beyond it. The differences show up in four places: whether any calls are free, what unit is charged, whether the price is fixed or depends on usage, and what happens when a request fails partway through. Compare those four things across providers rather than assuming the protocol makes them equivalent.
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What the ArcRouter free tier actually buys
ArcRouter’s documentation lists a $0 tier with these limits:
- Models: free models only. The provider states, “Free-tier users are always restricted to free models.” Access to paid models requires a paid call, not a larger free allowance.
- Rate limit: 20 requests per hour per IP, as stated in ArcRouter’s current documentation (accessed in 2026).
- Payment: none required on this tier. The free tier does not need a wallet.
The practical consequence is that a free-tier agent can test prompts, check output formats, and run low-volume jobs at no cost, but it cannot route heavier work to paid models without starting to pay. An agent that hits the hourly cap must wait or move to a paid route. Because the limit is per IP, agents sharing an outbound address share the same quota.
What ArcRouter’s paid tier costs
ArcRouter’s documentation describes MPP and x402 paid access at $0.001 to $0.015 per request. The price depends on the complexity class the request falls into. These are vendor-published prices, and the vendor says they are subject to change, so confirm them on the day you set a budget.
| Complexity class | Price per request (ArcRouter docs, 2026) |
|---|---|
| Simple | $0.001 |
| Medium | $0.002 |
| Complex | $0.005 |
| Reasoning | $0.012 |
| Premium | $0.015 |
| Council mode | 5× the price of the applicable tier |
Council mode, which runs several models together, is the most expensive option. A budget that assumes simple-tier pricing will be wrong by a factor of five if an agent switches a workflow into council mode. Set the cap with that multiplier in mind.
How Arcloak prices usage differently
Arcloak’s documented Arc example works on a different model. It uses an x402 upto flow on Arc mainnet. The client authorizes a ceiling, and the final charge depends on the tokens delivered. A call that generates fewer tokens than expected costs less than the ceiling; a call that stops early is charged for what was delivered. Arcloak’s buyer quickstart describes paid wallet-based calls and does not establish a free tier, and its quickstart does not list a full current price table. Use Arcloak’s pricing page for figures.
ArcRouter and Arcloak side by side
| Axis | ArcRouter (vendor documentation) | Arcloak (vendor documentation) |
|---|---|---|
| Free access | Free models only; 20 requests per hour per IP | Not stated: the buyer quickstart describes paid wallet-based calls and does not describe a free tier |
| Pricing unit | Per request, set by complexity class | Ceiling authorized up front; charge tied to tokens delivered |
| Fixed or usage-based | Fixed per complexity class (council mode 5×) | Usage-based within an authorized ceiling |
| Network and asset | x402 documented on Base in the product comparison page; Arc option shown in endpoint documentation | Arc mainnet with USDC |
| Authorization | Exact-amount authorization documented for x402 | One Permit2 approval for the documented upto flow |
| Settlement and refunds | Ceiling with batched refunds of the difference, as described in ArcRouter’s x402 docs | Charged for delivered tokens within the ceiling |
| Prompt privacy | Not stated in the sources reviewed for this article | Open-tier nodes run by third parties can see prompts in plaintext |
The table shows why the same “pay per call” label can mean different things. Read the settlement row closely before you assume a failed call is refunded or that a ceiling is the most you can be charged.
What authorizes a paid call on Arc
Paying for an Arc-based API call takes three pieces: a funded wallet, a payment client, and a policy the client enforces. Arcloak’s documented setup uses:
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problems- An Arc wallet holding USDC.
- The
@x402/fetchand@x402/evmpackages as the x402 client. - A single Permit2 approval for the documented
uptoflow.
Those are the packages and steps Arcloak documents for its own flow. Other providers may use different SDKs or schemes, so the exact setup has to come from the provider you are calling. The important point is where the limits live. Your payment client should enforce the asset, the network, and the per-payment maximum. Do not rely on a prompt that tells the model to stay under a budget. A model can ignore that instruction; a signing policy cannot be argued with.
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Settlement, failure, and who holds the risk
Arcus, which provides facilitator software for the payment side, documents this behavior: “Payment is settled only after your handler returns successfully. A failed request is never charged.” That is Arcus’s documented behavior for services built on its facilitator. It is not a rule that applies to every x402 service, and you should not assume it for an endpoint run by a different provider. For ArcRouter, the documented arrangement is a ceiling with batched refunds of any difference. For Arcloak, the charge follows the tokens delivered within the authorized ceiling. Before you run an agent unattended, test what happens when a job fails midway with the specific provider you have chosen, using a small budget.
Which chain you are actually paying on
ArcRouter’s product comparison page documents x402 on Base. Its separate endpoint documentation shows an Arc option. Those two statements do not conflict, but they do not mean every ArcRouter route accepts Arc. Read the network field in each 402 challenge and confirm that your wallet holds the asset on that network. An agent configured for Arc will fail or refuse to sign if the challenge names Base, and the reverse is also true.
Capping an agent’s USDC spend
Use these controls together rather than relying on any one of them:
- Wallet balance: keep only the USDC an agent is meant to spend in its payment wallet.
- Asset and network allowlist: configure the client to pay only in the expected asset on the expected network.
- Per-payment maximum: set a ceiling below which a single call is authorized, sized to the most expensive tier you expect to use. For ArcRouter, that is $0.015 per request, or $0.075 in council mode at the current list price.
- Total budget: cap cumulative spend for the run, not just per call, so repeated calls cannot add up unnoticed.
- Recipient check: confirm the payment destination matches the provider’s documented address before the first run.
- Max tokens: limit output length in the request so usage-priced calls stay within the ceiling you authorized.
When the budget is exhausted, the client should stop signing and surface an error to the workflow instead of retrying indefinitely. A retry loop around a 402 is the most common way an agent overspends.
Keeping prompts out of third-party hands
Arcloak’s documentation warns that in its open-tier setup, the node operators are third parties who can see prompts in plaintext. Treat any paid call routed through a third-party node as visible to that operator. Do not send API keys, customer records, or confidential documents through such a route unless the provider’s data handling has been checked separately and meets your requirements.
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