x402 Endpoint Buyer Preflight
Probe a public endpoint without paying, validate its x402 payment challenge and Base requirements, and check exact listing evidence in Coinbase Bazaar and 402index before a buyer authorizes payment.
Preview request
The preview path is rate-limited and does not charge. Production requests use the same parameters and return a standard x402 challenge when no payment signature is present.
curl --request POST \
"https://ai-data-marketplace-1042299154756.us-central1.run.app/api/v1/x402_endpoint_preflight?preview=true" \
--header "content-type: application/json" \
--data '{"url":"https://example.com/api/paid","method":"GET"}'Input contract
| Parameter | Type | Required | Description |
|---|---|---|---|
url | string | Yes | Public HTTP or HTTPS endpoint to inspect without paying. |
method | string | No | GET, HEAD, or POST. Defaults to GET. |
request_body | object | No | Optional JSON body for a POST probe. Payment credentials are never forwarded. |
Example deliverable
This is the documented response shape, not a promise that live values will match the example. The paid request returns current or declared-source results using the same contract.
{
"success": true,
"ready_for_payment": true,
"decision": "payment_challenge_is_structurally_ready",
"payment_requirements": [],
"discovery": {
"coinbase_bazaar": {
"checked": true,
"exact_match_count": 1
}
}
}Why this offer exists
A no-payment x402 challenge and directory preflight before an agent authorizes a purchase.
Buyer searches: x402 endpoint verification, payment challenge check, buyer preflight, x402 trust.
Launch price: 0.005 USDC per complete paid result. The free preview verifies the live contract and response shape before a wallet is asked to pay.
Purchase decision
Buy when: the active task needs this product's structured result, its declared source and freshness are sufficient, and 0.005 USDC is within the buyer's authorized per-request limit.
Skip when: a cached result is sufficient, the source or fields do not satisfy the task, or the buyer has not authorized payment. Do not bypass wallet, budget, or user-approval policy.
Guaranteed response metadata
Every successful product response identifies how the result was produced. Product-specific output fields are documented in the paid OpenAPI contract and can be inspected through the preview request where available.
{
"marketplace_metadata": {
"data_mode": "live_source",
"billable": true,
"availability": "operational",
"source": "live endpoint probe, Coinbase x402 Bazaar discovery, and 402index directory"
}
}Agent payment flow
Fast path: install the public MCP package, configure a dedicated low-balance Base buyer wallet and a maximum per-request spend, then call this tool with auto_pay: true. The client handles the challenge, local signature, settlement, and retry in one tool call.
npx -y dopaminedesk-ai-data-marketplace-mcp
X402_AUTO_PAY=true
X402_EVM_PRIVATE_KEY=<dedicated buyer wallet key>
X402_MAX_PAYMENT_USDC=0.25
tool input: { "auto_pay": true }Manual path: request the product, read the base64 PAYMENT-REQUIRED challenge, sign with any compatible x402 v2 client, and retry with PAYMENT-SIGNATURE. A successful response includes PAYMENT-RESPONSE.