Does this pay the third-party URL?

No. It fetches once to read unpaid requirements. Your agent still decides whether to pay that seller.

GET only. POST responds 405 method_not_allowed.

When am I not charged?

Unreachable upstream responds 503 and is not charged. invalid_url after pay (400) is not settled.

Is payTo OFAC match clearance?

No. Exact match is informational only. No match does not mean the wallet is clean.

Docs / x402 seller preflight

How do I preflight another x402 URL before my agent pays it?

Meridian by MioDio fetches a caller-supplied https URL once and reports its unpaid x402 payment requirements (scheme, network, asset, amount, payTo type, OFAC exact match) for $0.005 USDC on Base. Informational, not advice; unreachable targets are 503 and not charged.

What is reported

Paid 200 is an x402_preflight card: status, as_of, url, disclaimer, http (status, redirected, location.untrusted_url), x402 (valid, version, resource.url), accepts[] (scheme, network_claimed, network_caip2, network_form, asset, amount_atomic, amount_usd, pay_to, pay_to_type.kind, ofac.match), bazaar, flags, optional errors. Parsed unpaid x402 payment requirements when present: scheme, network, asset, amount, payTo type, and OFAC exact match on payTo. Any HTTP response from the target (including 500, 404, 302, or 200 with no 402) is a charged 200 with status partial or the parsed result.

Query parameter rules

Query url (required after payment): absolute https URL, port 443, at most 2048 characters
Validated after payment; unpaid probes without url still return 402

Call it

curl -i "https://meridian.miodiollc.com/v1/x402-preflight?url=https://www.example.com/"
# POST -> 405 method_not_allowed (preflight is GET)

Unpaid -> HTTP 402 + PAYMENT-REQUIRED.

Price and settlement edge cases

$0.005 USDC on Base (~5000 atomic). Network eip155:8453. Asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913. payTo 0x4DA1ED782BD61BaE9AdD5a5CaBbCf32f767f8d7F.

400 invalid_url after pay: not settled
DNS / timeout / TLS failure: 503 upstream_unavailable, not charged
Any HTTP response from the target: charged 200 with partial or parsed result

What it does NOT do

Meridian by MioDio never holds keys, does not sign user transactions, and does not move funds.
Not financial, legal, or compliance advice. Screens, drift, and simulation are informational and point-in-time where that applies.
Not a substitute for a compliance program.
No MCP server and no SDK are available today.

Unpaid calls return HTTP 402 with PAYMENT-REQUIRED. Retry with PAYMENT-SIGNATURE.

FAQ

Does this pay the third-party URL?: No. It fetches once to read unpaid requirements. Your agent still decides whether to pay that seller.
Which HTTP method?: GET only. POST responds 405 method_not_allowed.
When am I not charged?: Unreachable upstream responds 503 and is not charged. invalid_url after pay (400) is not settled.
Is payTo OFAC match clearance?: No. Exact match is informational only. No match does not mean the wallet is clean.