x402 Preflight

For x402 API developers · read only

Added x402 to your API? Find integration problems before your customers do.

Check your live endpoint's payment configuration, discovery metadata, schemas, and compatibility signals. Get evidence of what's wrong and recommendations for fixing it. Start free; get a technical audit for $0.05 or a diagnostic report with prioritized fix recommendations for $5.

Check my endpoint — free See an example diagnostic
  • Free check: no wallet needed
  • No payment headers forwarded
  • No automatic spending

Read-only checks. No test purchase. Does not verify settlement or paid delivery. No code changes or guaranteed marketplace indexing.

Free endpoint check

Check your live x402 payment challenge

Paste your public HTTPS endpoint. No wallet or test payment is needed. The server performs bounded HTTPS probes only. Targets and every redirect are checked against private and reserved networks.

The price limit is your comparison policy, not our service fee. A price-limit BLOCK does not establish that your integration is broken; ALLOW does not certify settlement or paid delivery.

Separate human review · legacy service routes

Need a separate human readback?

These legacy offerings are not included in the $5 automated diagnostic. The GET intakes serve a valid x402 challenge when the target and goal are present. They create an order only after payment settles.

Quick review

Focused challenge readback, blockers, proof commands, and next patch.

Open quick review

Machine-readable report

Inspection result

Ready 
Submit your public HTTPS x402 endpoint to see its challenge, comparison policy checks, evidence, and claim boundary.

Launch diagnostics for API developers

Check free. Audit for $0.05. Get a fix report for $5.

Paid services use native USDC on Base. Your wallet pays for our report, not the target API. The live 402 challenge determines the price.

  1. 01

    Free endpoint check

    Is your endpoint advertising payment correctly? Inspect its live challenge and caller-selected comparison policy. ALLOW, CAUTION, BLOCK, and UNKNOWN are policy decisions, not launch certifications. No wallet required.

    FREE POST /api/preflight/inspect
  2. 02

    Technical audit

    What configuration or compatibility issues can we detect? Receive a structured report immediately, with payment configuration, discovery metadata, schema, CORS, redirect, cache, and policy evidence.

    POST /api/x402/preflight/audit
  3. 03

    Diagnostic report

    What should you fix first, and why? Buy an asynchronous report with findings, evidence, and prioritized fix recommendations in JSON/Markdown. Optional signed HTTPS callback. No implementation or human consultation included.

    POST /api/x402/preflight/remediation

For developers, agents, and CLI users

Check your integration before launch

Replace the example resource_url with your public HTTPS endpoint. Inspect for free with curl; paid calls need an x402-capable client and a wallet funded with native USDC on Base. These are read-only diagnostics, not paid-delivery tests.

1. Check your endpoint for free

Try our snapshot endpoint first, then substitute your own URL. This check does not pay the endpoint being inspected.

curl --fail-with-body https://x402.chikocorp.com/api/preflight/inspect \
  -H 'Content-Type: application/json' \
  -d '{"resource_url":"https://x402.chikocorp.com/api/x402/market/crypto-snapshot?limit=1","method":"GET","expected_network":"eip155:8453","max_price_usd":0.05}'

2. Get deeper launch diagnostics

Configure AgentCash following its documentation and fund its wallet. Discovering endpoints is not a purchase:

npx agentcash@latest discover https://x402.chikocorp.com

These fetch commands authorize real payments. Choose an audit ($0.05) or automated diagnostic ($5); they are separate purchases.

Paid audit command — $0.05 
npx agentcash@latest fetch https://x402.chikocorp.com/api/x402/preflight/audit \
  -m POST \
  -b '{"resource_url":"https://x402.chikocorp.com/api/x402/market/crypto-snapshot?limit=1","method":"GET","expected_network":"eip155:8453","max_price_usd":0.05}'
Paid diagnostic command — $5 
npx agentcash@latest fetch https://x402.chikocorp.com/api/x402/preflight/remediation \
  -m POST \
  -b '{"resource_url":"https://x402.chikocorp.com/api/x402/market/crypto-snapshot?limit=1","goal":"Identify x402 launch configuration and browser compatibility issues, with prioritized fix recommendations","response_format":"both","language":"en"}'

Set max_price_usd to the target price you want to allow; it does not cap our service fee or certify your integration. Plain curl does not sign x402 payments.

3. Retrieve your diagnostic

The paid order receipt contains review.resultUrl, review.reportUrl, and a private review.accessToken. Retrieval requires no additional payment.

curl --fail-with-body '<review.resultUrl from your receipt>' \
  -H 'Authorization: Bearer <review.accessToken from your receipt>'

Use review.reportUrl the same way for Markdown. HTTP 202 means the review is running: poll the result URL, not the paid intake. Do not blindly retry a timed-out purchase.

For MCP, connect a payment-enabled client to https://x402.chikocorp.com/mcp. Wallet signing and explicit purchase approval belong to that client.

Illustrative output · fictional seller

See what's wrong, who it affects, and what to fix

This is a sample, not a real customer order or audit. GET exposes a payment challenge, but OPTIONS returns HTTP 405. Browser-based clients may fail preflight; that does not imply every x402 client fails.

{
  "status": "completed",
  "verdict": "needs_changes",
  "summary": "GET exposes a payment challenge, but OPTIONS returns HTTP 405. Browser-based clients may fail preflight.",
  "next_steps": ["Configure OPTIONS/CORS for the required origin, method, and payment headers, then rerun the check."]
}

This is an excerpt. Read the full sample JSON for checks, findings, evidence, recommendations, and limitations. A real review can be inconclusive; it cannot guarantee settlement or seller trust.

Evidence, not endorsement

Launch evidence, not launch certification

CHECKS

Observable now

  • HTTP 402 challenge and x402 version
  • Scheme, network, asset, amount, and receiver
  • Bazaar, OpenAPI, llms.txt, and agent metadata
  • CORS, redirects, content type, cache, latency, and size
BOUNDARY

Not guaranteed

  • Seller identity, intent, or future availability
  • Contract safety or downstream business outcome
  • That a later payment will verify or settle
  • Paid response delivery or actual marketplace indexing
  • That the resource remains unchanged after expiry

Agent integration

Discover once, call through the interface you already use

Built primarily for endpoint owners. Buyers can still use the same read-only checks before authorizing a purchase.

Machine-readable surface: /openapi.json · /llms.txt · /.well-known/x402.json · /.well-known/agent.json · POST /mcp. These are files and protocol endpoints for agents, not pages to browse.

HTTP + OpenAPI

Strict request, report, receipt, and error schemas are published at the canonical contract.

Open /openapi.json

Remote MCP

MCP (Model Context Protocol) is how an agent runtime discovers and calls tools. Point a payment-enabled MCP client at this endpoint and it lists exactly the same three capabilities, with no labs tools: the free check, the 0.05 USDC audit, and the 5 USDC diagnostic order. A browser request returns 405 by design — it is a protocol endpoint, not a page.

POST /mcp

x402 + Bazaar

The unpaid 402 response remains authoritative for live price, network, asset, and receiver.

Open x402 metadata
Labs and legacy endpoints

Existing wallet readiness, market data, weather, repository snapshots, marketplace adapters, and signing helpers remain available for current consumers. They are compatibility surfaces, not primary x402 Preflight capabilities.

See compatibility routes in the manifest