X402 Seller MCP Server

x402-seller — rug protection for autonomous trading agents

Live: https://x402-seller-m8nx.onrender.com · Base mainnet · no signup, no API key — pay per call in USDC via x402

Your agent is about to ape into a token. One bad ape costs its whole position. This API answers "is this a rug?" in one call, with evidence:

• Composite rug score — GoPlus static analysis fused with a live Honeypot.is buy/sell simulation (it actually executes a simulated trade), a serial-rugger check, hard honeypot gates, and a needs_review flag when the two engines disagree.
• Solana too — dual-engine (GoPlus-Solana + RugCheck): mint/freeze authorities, holder concentration, LP burn. Different chain, different rug physics, same design.
• Liquidity-drain detector — we poll pool reserves over time and answer "is liquidity leaving right now?" — the earliest sign of a rug in progress. This time-series exists nowhere for free; you can't backfill history you didn't collect.
• Public self-graded track record — every 30 minutes we score fresh Base launches with the exact paid scorer, then grade ourselves against what actually happened. Hits and misses published. Evidence, not claims.

Try it free, right now

# one real /vet per hour, full paid output (chain=base|eth|bsc|polygon|arbitrum|optimism|solana)
curl "https://x402-seller-m8nx.onrender.com/demo/vet?chain=eth&address=0x6982508145454Ce325dDbE47a25d4ec3d2311933"

# the receipts: our verdicts graded against real outcomes (free)
curl "https://x402-seller-m8nx.onrender.com/track-record"

# sample output for every endpoint (free)
curl "https://x402-seller-m8nx.onrender.com/examples"

Buy with three lines (any x402 client)

import { wrapFetchWithPayment } from "@x402/fetch";
import { privateKeyToAccount } from "viem/accounts";

const payFetch = wrapFetchWithPayment(fetch, privateKeyToAccount(process.env.PK));
const r = await payFetch("https://x402-seller-m8nx.onrender.com/vet?chain=base&address=0x…");
// 402 → auto-pay USDC on Base → data. That's the whole integration.

Endpoints

Free: / · /demo/vet · /track-record · /examples · /catalog · /llms.txt · /.well-known/x402.json · /.well-known/agent.json · /openapi.json · /health · /stats

Verdict-first flat JSON everywhere: read field 1, act. Reasons included for audit. Malformed requests are rejected before the paywall — your agent never pays for a doomed call.

Why pay when the underlying sources are free?

Honest answer: the snapshots are free — the judgment and the history are not.

1. The liquidity time-series is self-collected. There is no free API for "liquidity 1 hour ago."
2. The composite catches what single sources miss: static-only scanners miss simulated sell-traps; simulation-only misses authority/mint risks. Disagreement between engines is itself signal (needs_review).
3. One $0.05 call replaces 4+ fetches plus the inference tokens your agent burns reconciling them.
4. It's keyless. Your agent can't fill signup forms — it can pay 5 cents.
5. The track record is public, misses included. Judge the scorer by its record, not this README.

Use as an MCP tool (Claude Code, Cursor, any MCP client)

Rug-checking + launch radar as agent tools. Two ways in:

Hosted (no install) — add the remote MCP server, free demo tools out of the box:

claude mcp add --transport http x402-seller https://x402-seller-m8nx.onrender.com/mcp

Tools: vet_token · launch_radar · rug_check · track_record · catalog (shared free daily demo budget; unlimited via the paid HTTP API). Published to the official MCP Registry as io.github.wyattpalm2-eng/x402-seller.

Local (self-hosted, pays for itself) — clone and run the stdio server, add a burner key for unlimited paid calls:

git clone https://github.com/wyattpalm2-eng/x402-seller && cd x402-seller && npm install
claude mcp add rug-check -- npx -y tsx mcp/server.mts

Tools: vet_token · launch_radar · rug_check · liquidity_trend · market_brief · track_record · catalog.

• No config: works immediately — vet_token routes through the free demo (1 real call/hour), track_record/catalog are always free.
• X402_BUYER_PK=0x… (a burner wallet with a few dollars of USDC on Base): every tool goes unlimited, settling ~$0.01–0.05 per call via x402 automatically. No account anywhere.
• X402_SELLER_URL=…: point the tools at your own self-hosted instance.

Run your own

npm install && npm start                            # localhost:4021, Base Sepolia by default
NETWORK=eip155:8453 PAY_TO=0xYourWallet npm start   # mainnet — keyless facilitators, no CDP account needed

One-click deploy: render.yaml blueprint. The server registers three redundant keyless facilitators (PayAI, xpay, 0xarchive) on mainnet — no facilitator account required.

Prove the full payment loop end-to-end (needs a burner wallet with ~$1 USDC on Base):

BUYER_PK=0x<burner-key> npx tsx scripts/selfbuy.mts

Architecture notes

• Node/TS + Express + @x402/express. Three redundant facilitators registered in one x402ResourceServer — any one advertising Base-mainnet exact keeps settlement alive.
• Stale-while-revalidate cache with in-flight dedup in front of every upstream: a paying buyer never blocks on a cold upstream or eats a 502 while a recent value exists.
• SSRF-safe: chain allowlists, strict address regexes, encodeURIComponent everywhere, upstream errors never echoed to clients. Receive-only — the server holds no private key.
• Junk never billed: sources throw on non-finite prices/empty payloads → uncharged 502; malformed input 400s before the paywall.
• /track-record and /onchain/liquidity ledgers are in-memory + JSONL on free-tier ephemeral disk: depth compounds while the service runs and resets on redeploy. Documented, not hidden.

Layout

src/
  index.ts       server: paywall wiring, free routes, demo, storefront
  safety.ts      EVM composite rug score (GoPlus × Honeypot.is + agreement factor)
  solsafety.ts   Solana composite (GoPlus-Solana × RugCheck)
  history.ts     liquidity time-series poller + drain detector
  record.ts      the self-graded public track record
  composites.ts  /vet and /brief answer endpoints
  crypto.ts      on-chain aggregator (DexScreener/GeckoTerminal/DeFiLlama)
  funnel.ts      who viewed (402) vs who bought — demand telemetry
scripts/
  selfbuy.mts    one-command real x402 purchase (settlement proof)

MIT. Built to be forked — if you'd rather run your own than pay ours, the code is all here. The moat isn't the code, it's the collected history and the graded record.