x402-native, pay-per-call. Two HTTP tools an agent pays for inline — no accounts, no keys held. Quotes on Base, Polygon & Arbitrum — pay in USDC from any of them or Solana.
x402-nativemultichaindecision-grade
the gap
A wallet guard like Blockaid tells an agent whether a transaction is malicious — can I sign this? It can't tell the agent should I trade this? — what price actually fills under size, and whether the token is an economic trap. Plexa answers the economic question.
two endpoints, one engine
POST /v1/quote$0.02
Executable liquidity under a given size: real fill price (not mid/spot), price impact (bps), realizable depth, per-leg route, worst-case slippage, confidence. Priced from canonical on-chain quoters, on Base, Polygon & Arbitrum.
POST /v1/pretrade/check$0.05
Economic-safety verdict — ok / caution / avoid — with reasons and confidence. Weighs liquidity structure, holder concentration, token age, fee-on-transfer / honeypot fingerprints, oracle sanity, in context. Plus an executable quote. Analysis runs on Base today — you can pay from any of the four payment rails, but the flags are Base-tuned, so another chain value answers 422 rather than guessing.
example
// POST /v1/pretrade/check{"token": "0x4200000000000000000000000000000000000006", "sizeUSD": "5000", "chain": "base" }// →{"chain": "base",
"verdict": "ok",
"confidence": "high",
"reasons": ["major vetted token — individual flags treated as notes"],
"quote": {"direction": "buy", "executablePrice": 0.000530143806060766, "priceImpactBps": 6.03 },
"disclaimer": "Informational economic-safety signal, not financial advice. Flags are heuristics over on-chain state and can miss novel traps; absence of flags is not a guarantee of safety."
}
executablePrice is token per 1 USDC at the requested size — here 0.00053 WETH per USDC, i.e. the realizable fill, not a mid quote.
connect & configure
As an MCP tool
Add the Plexa MCP server to any agent (Claude Code / Claude Desktop / any MCP host). It exposes plexa_quote and plexa_pretrade_check. Payment is handled automatically via x402 from a wallet you configure — Plexa never sees the key.
Direct HTTP (x402)
Any x402 client works (e.g. @x402/fetch). Call the endpoint; on 402 the client signs a USDC payment (EIP-3009) and retries — the response is served only after on-chain settle. Pass chain: base / polygon / arbitrum.
Use a dedicated, low-balance wallet. This key signs payments; it is not an API key. Keep it in your environment and let the host expand ${AGENT_WALLET_KEY} — if your MCP host does not support expansion, put the literal value in a file with restrictive permissions and never commit it. Plexa never sees the key: it stays in your client.
Live on npm: @getplexa/mcp — run with npx -y @getplexa/mcp. The public API is live at api.getplexa.com.
open-source reference agent
See Plexa in action
A complete, MIT-licensed reference agent — a dust consolidator that discovers small token balances, checks each through Plexa, and swaps the safe ones. Client-only: it uses nothing but the public API, so it doubles as a working integration pattern you can fork.