x402 · MCP · X Layer
Pay-per-call market data for tokenized equities
An MCP server and REST API for NVDA, SPY and TSLA xStocks on X Layer. Quotes against live Uniswap v3 liquidity, market-session checks and unsigned trade plans, each paid per call with x402. No account needed.
→ tools/call quote {"symbol":"NVDA","side":"buy","size":"1000"}← payment required · $0.01 USD₮0 · eip155:1952→ tools/call quote + _meta["x402/payment"] (EIP-3009 signature)← settled · receipt in _meta["x402/payment-response"]{"fill": { "pay": "1000 USDG", "receive": "4.3672 shares (wNVDAx)","avgPricePerShare": 228.98, "priceImpactBps": 5.6 },"reference": { "venue": "OKX spot", "onchainEdgeBps": 3.6 },"data": { "network": "eip155:196" }}
Real xStocks and real liquidity live here, so every read and every generated transaction points at mainnet.
Try it with free faucet USD₮0. Nobody spends real money on a demo; mainnet payments are configured and switched off.
How it works
Priced per call, paid in the call
x402 turns a tool call into a purchase. The agent signs, the facilitator settles, the result comes back with a receipt.
Your agent calls quote over MCP or REST. catalog is free; initialize and tools/list never ask for payment.
An unpaid call returns x402 payment requirements: the amount, USD₮0 on X Layer testnet, and where to pay.
The agent signs an EIP-3009 authorization from any wallet. No OKX account, no gas.
The facilitator verifies and settles on-chain. The result arrives with the receipt.
Tools
Four tools, priced per call
Same tools over MCP and REST. Refused calls are never charged.
What Roundlot covers and what each tool costs.
- NVDA, SPY and TSLA xStocks
- Token and ERC-4626 wrapper addresses
- Uniswap v3 venue, OKX reference market
- Data vs payment network
Is the US market open, and what that means for the price.
- NYSE phase, next open and close
- Holidays and early closes
- OKX pricing regime off-hours
- Issuer pause, multiplier changes
The fill for a buy or sell against live liquidity.
- Size in USD or shares
- Average price per share
- Price impact vs the pool mid
- Edge vs crossing the OKX book
Ordered, unsigned transactions to execute it.
- Approve, wrap, swap, unwrap
- Slippage limits and a deadline
- Skips approvals you already gave
- You sign; Roundlot holds nothing
Under the hood
How the numbers are made
Only wrapped xStocks trade
On X Layer the liquid Uniswap v3 pools pair the ERC-4626 wrappers with USDG or USDC. Quotes route through the wrapper; plans add the wrap or unwrap step.
Per-share, not per-token
A wrapped token carries a corporate-action multiplier, so pool prices are divided by the wrapper rate before they are compared with OKX. Without it, SPY looks 45 bps rich.
No partial fills dressed up as quotes
If a size would run the pool out of in-range liquidity, the quote is refused and nothing is charged.
Prices have a regime
xStocks trade around the clock; outside US hours the price is last close plus an estimate. session says which one you are looking at.
Connect
One URL for MCP, plain HTTP for the rest
{ "mcpServers": { "roundlot": {
"type": "http",
"url": "https://api.roundlot.0xo.in/mcp"
} } }# free
curl -X POST https://api.roundlot.0xo.in/v1/catalog
# paid: answers 402 with PAYMENT-REQUIRED
curl -i "https://api.roundlot.0xo.in/v1/quote?symbol=NVDA&side=buy&size=100"FAQs
Questions
The short answers. The docs and the README have the long ones.
Give your agent a market it can pay for
Pay-per-call market data and trade plans for tokenized equities on X Layer. Built for OKX Dev Day 2026.