Payload
Payload · Payment Diagnostics
Your x402 payment failed.
callx402 finds out why.
When an x402 payment fails, the error rarely tells you which layer broke: the challenge, the wallet, the facilitator, or the settlement. callx402 is a diagnostic toolkit that investigates the failure and returns structured evidence, a plain language explanation, and the safest next step.
callx402 diagnoses and explains. It does not hold funds, it does not execute payments for you, and it never promises that a failed payment can be recovered.
FREE LOCAL TOOLS · PAY PER ACTION, NO SUBSCRIPTION · STRUCTURED EVIDENCE FOR EVERY RESULT
How it works
Start free on your own machine. Go hosted when you want us to run it.
Three steps between a failed payment and an answer you can act on.
Step 1
Run the free status check
Install the npm package and run npx callx402. The free x402_status tool reads your setup and reports what it finds, locally, in seconds. No account, no payment.
Step 2
Diagnose locally
The package ships six local MCP tools (status, diagnose, evidence, explain, recover, resolve) that work against your own x402 payment failure. They are read only and never move money.
Step 3
Or call a hosted action
Ask the free quote endpoint for the exact price, then call a hosted diagnostic action on the Payload rail and pay per action in USDC on Base. You get structured evidence and an explanation back.
Guessing
A raw error code, a retry, and a hope.
Nothing records what the evidence showed, so the same failure burns the same hours next time.
callx402
Which layer broke, classified from the evidence
What the receipt actually proves about a payment
Whether a retry is safe before you risk a duplicate
Every result is structured evidence you can keep with the incident record.
Use cases
Built for the failures that eat afternoons
If your product sells through x402, these are the incidents that decide whether a customer stays. callx402 gives each one a fast, evidence based answer.
The facilitator said no
A facilitator error is not an explanation. Settlement interpretation reads the response and tells you what it actually means.
You paid and nothing arrived
Verify the receipt against its evidence before you pay again. Know what settled, what did not, and what to do next.
Is a retry safe?
A blind retry can pay twice. Duplicate payment risk checks the evidence first, so the second attempt is a decision, not a gamble.
An error you cannot decode
Raw payment errors are written for machines. Explain error turns them into plain language a developer can act on.
Before you ship
Preflight checks a planned payment path before real money depends on it, so the first failure happens in testing, not in production.
Your agent hit a wall
Autonomous buyers fail quietly. callx402 gives the operator, human or agent, a structured read on what stopped the payment.
Pricing
Free locally. Pennies when hosted.
The npm package and its local tools are free. Hosted actions are pay per use, with no subscription and no balance to top up. The quote endpoint is free and returns the exact price for any action before you pay anything.
Free: the local tools
The npm package runs on your machine: status, diagnose, evidence, explain, recover, and resolve. Read only, no account, no payment, and the free x402_status check is the fastest way to see whether callx402 understands your failure.
Hosted: pay per action
Payload runs the diagnosis on the rail and returns structured evidence and an explanation. Pay in USDC on Base through the x402 challenge each action returns, or by card through the rail checkout endpoint.
| Hosted action | What it returns | Card | x402 (USDC on Base) |
|---|---|---|---|
| diagnose | A structured diagnosis of a failed x402 payment | $2.00 | $0.10 |
| preflight | A check of a planned payment before it runs | $1.00 | $0.05 |
| verify_receipt | Verification of a payment receipt against its evidence | $1.00 | $0.05 |
| explain_error | A plain language explanation of a raw payment error | $0.50 | $0.025 |
Hosted actions are charged via x402 at one twentieth of the card schedule above. More hosted actions, including failure_classification, settlement_interpretation, duplicate_payment_risk, resolve, and recover, are priced on the same schedule; ask the free quote endpoint (GET https://payload-rail.fly.dev/v1/callx402/quote) for the exact price of any action before you commit. Call an action unpaid (POST https://payload-rail.fly.dev/v1/callx402/actions/{action}) and it answers with its x402 challenge: the exact USDC amount and the payTo on Base.
Honest limits: hosted purchases settle through Payload's signed redemption flow rather than a generic x402 facilitator, so facilitator only clients cannot complete a hosted purchase; the free local tools are the no payment alternative. No diagnosis covers every failure, and no result is a promise of recovery.
Running x402 at volume, or wiring diagnostics into your own product? Contact us and we will scope it with you.
FAQ
Straight answers
What callx402 does, what it does not do, and exactly how paying for it works.
What does callx402 do?
Is callx402 free?
Does callx402 hold or move my money?
Can callx402 recover a failed payment?
How do I pay for a hosted action?
Can I use callx402 as an MCP server?
What support is included?
Documentation
Verify it yourself
The package, the endpoints, and the pricing quote are all public. Run the free check before you believe a word of this page.
A failed payment is a question.
callx402 is how you answer it.
Support: contact@payloadhq.dev