What is the window max?

window_minutes is an integer from 1 to 120 (OpenAPI maximum).

Docs / On-chain USDC payment check

How do I verify a Base USDC x402 payment on-chain?

Meridian by MioDio's POST /v1/payment-check reads a Base USDC Exact authorization or Transfer on-chain: nonce used, matching transfers in a 120-minute window or less, and confirmations, for $0.005 USDC via x402. Informational and point-in-time; if every on-chain read fails the call is 503 and not settled.

What is checked

Paid 200 is a payment_check card: status, nonce_used, matching_transfers, duplicate, txs[], tx (hash, found, confirmations, block_number) or null, latest_block, confirmations_min, as_of, partial, notes[], disclaimer.

Whether that payment authorization was already used (nonce_used)
How many matching transfers exist in the window (matching_transfers; duplicate is true when more than one)
Confirmations on the tx (tx.confirmations)

Never exposes RPC URLs. Never signs or moves funds.

Request body

JSON properties (OpenAPI):

payer (string)
nonce (string)
pay_to (string)
amount (string)
window_minutes (integer, 1 to 120)
tx (string)

Send a tx hash, and/or payer + nonce, and/or payer + pay_to + amount (cheat sheet).

Call it

curl -i -X POST "https://meridian.miodiollc.com/v1/payment-check" \
  -H 'content-type: application/json' \
  -d '{"payer":"0x0000000000000000000000000000000000000001","nonce":"0xabababababababababababababababababababababababababababababababab","pay_to":"0x4DA1ED782BD61BaE9AdD5a5CaBbCf32f767f8d7F","amount":"5000","window_minutes":60}'

Unpaid -> HTTP 402 + PAYMENT-REQUIRED. 503 upstream_unavailable if every read fails (not settled). Partial 200 when some chain reads fail (charged).

Free sibling: GET /v1/payment/status

GET /v1/payment/status covers Meridian's own payments by tx or payer+nonce (30/min per IP). It does not return receipt_id. On a miss, use paid POST /v1/payment-check.

Price

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

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 move funds?: No. On-chain read only.
What is the window max?: window_minutes is an integer from 1 to 120 (OpenAPI maximum).
How do I check Meridian's own payment status without paying?: GET /v1/payment/status (30/min per IP). It does not return receipt_id. On a miss, use paid POST /v1/payment-check.