x402 — the live x402 test endpoint

Agentic payments on GSC-Marketplace — a live x402 endpoint any AI Agent can settle against.

Operated by GreenCore Solutions Corp. · Microsoft AI Cloud Partner · Open protocol

What x402 is

x402 is an open payment protocol for the web's HTTP 402 status: a server answers a request with 402 and a machine-readable statement of terms; the client signs a transfer authorization; the server verifies and settles it and answers 200. The protocol is open, stewarded under the Linux Foundation, and transport-agnostic — an AI Agent pays without an account, a checkout, or a human in the loop.

What this endpoint does

gsc-marketplace.ai/api is the ecosystem's test counterparty. A developer points an x402-capable agent at it and proves the whole stack end to end with a real settlement on Base: the 402 challenge, the signed authorization, the facilitator settlement, and a signed receipt that verifies offline against this host's JWKS. The receipt resolves forever at /x402/receipt/ plus its nonce — the nonce is the claim ticket. Every settlement also emits an IA-MESSAGE to the transaction MCP, where it appears as a read-only desk row beside the RFQs.

The exchange

# 1 · Ask for the resource — the server answers 402 with the terms (x402 v2) $ curl -i "https://gsc-marketplace.ai/api" HTTP/2 402 PAYMENT-REQUIRED: base64(JSON body below) { "x402Version": 2, "error": "PAYMENT-SIGNATURE header is required", "resource": { "url": "https://gsc-marketplace.ai/api", "description": "x402 test counterparty — prove your payment stack end to end with a real settlement on Base.", "mimeType": "application/json" }, "accepts": [ { "scheme": "exact", "network": "eip155:8453", "amount": "5000", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "maxTimeoutSeconds": 60, "extra": { "assetTransferMethod": "eip3009", "name": "USD Coin", "version": "2" } } ], "extensions": {} } # the receive address (payTo) is stated in the live 402 payload only — never on this page # 2 · Your agent signs an EIP-3009 transferWithAuthorization for the exact amount and retries $ curl -i "https://gsc-marketplace.ai/api" -H "PAYMENT-SIGNATURE: base64(PaymentPayload)" # 3 · The server verifies and settles through the facilitator and answers 200 with a signed receipt HTTP/2 200 PAYMENT-RESPONSE: base64(SettlementResponse) { "confirmation": "x402 settlement confirmed — your stack works end to end", "nonce": "32 hex characters — the claim ticket", "receipt_url": "https://gsc-marketplace.ai/x402/receipt/ plus the nonce", "signature": { "alg": "EdDSA", "kid": "gsc-x402-receipts-2026-08" } }

The 402 challenge

The payload is protocol fact — it is the terms. Network eip155:8453 (Base) · asset USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) · scheme exact · EIP-3009 transferWithAuthorization · 60-second window. Amount and receive address are stated in the payload only.

Machine Surfaces

/api · /x402/receipt/{nonce} · /x402/jwks.json · /x402.json · /llms.txt · /.well-known/agent-card.json · /.well-known/mcp/server-card.json · /.well-known/ai-catalog.json

Identity Beacons