@getplexa/mcp — Plexa MCP server

A Model Context Protocol server that gives any MCP client (Claude Desktop, Cursor, your own agent) two economic-safety tools from Plexa — the x402-native economic-safety layer for trading agents — paid per call in USDC, no accounts:

Tool	Wraps	Price	Returns
plexa_quote	POST /v1/quote	$0.02	Executable fill price under size (not mid/spot), price impact (bps), realizable depth, per-leg route, worst-case slippage, confidence — from canonical on-chain quoters on Base, Polygon & Arbitrum.
plexa_pretrade_check	POST /v1/pretrade/check	$0.05	Economic-safety verdict ok / caution / avoid + reasons + confidence, plus an executable quote. (Base-only today.)

It is a thin client of the public API (https://api.getplexa.com) — it pays a 402 automatically, signs the USDC authorization locally with your wallet, and never sees your key. The liquidity engine stays behind the API.

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Why

A generic wallet guard answers "can I sign this transaction?". It can't answer the economic question an automated trader actually needs: what price will this swap really fill at under my size, and is this token a trap (rug / honeypot / thin liquidity)? Plexa answers both. This package puts those answers one tool-call away inside any MCP-speaking agent.

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Install

Nothing to install — point your MCP client at the package via npx. It is fetched and run on demand.

Claude Desktop

Add to claude_desktop_config.json (Settings → Developer → Edit Config):

{
  "mcpServers": {
    "plexa": {
      "command": "npx",
      "args": ["-y", "@getplexa/mcp"],
      "env": {
        "PLEXA_BASE_URL": "https://api.getplexa.com",
        "AGENT_WALLET_KEY": "0x<your funded wallet private key>",
        "CHAIN": "base"
      }
    }
  }
}

Cursor

Add to ~/.cursor/mcp.json (or Settings → MCP → Add) — the same mcpServers block as above.

Restart the client. You should see the plexa_quote and plexa_pretrade_check tools available.

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Configuration

All configuration is via environment variables (set in the env block of your MCP config):

Variable	Default	Notes
PLEXA_BASE_URL	https://api.getplexa.com	The public API. The real URL — not a secret.
AGENT_WALLET_KEY	(none)	Required to pay. Funded wallet private key — pays per call and signs locally. Plexa never receives it. Without it, tools return a clear 402.
CHAIN	base	base | polygon | arbitrum. The chain your wallet is funded on; quotes and payment default to it. plexa_pretrade_check is Base-only today.

Funding. Use a dedicated, low-balance wallet with a little USDC on CHAIN to pay per call (quotes $0.02, checks $0.05). The wallet signs an EIP-3009 USDC authorization per request; Plexa returns the result only after the payment settles on-chain (settle-before-serve).

Your key is a secret. Prefer your MCP client's secret storage if it has one. Never commit it.

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How payment works (x402 in MCP)

MCP has no native payment. This server acts as an x402 client: it wraps fetch, so when Plexa replies 402 Payment Required it reads the payment requirements, signs a USDC authorization with your wallet (locally), and retries. The signed authorization is the only thing that leaves your machine — never the key. Payment is made on CHAIN, so you fund one wallet on one chain.

If no AGENT_WALLET_KEY is set, the tools return an honest 402 error explaining a funded wallet is needed — they never fabricate a result.

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Example

Once configured, just ask your agent naturally — it will call the tools:

"Before I buy this token 0x… on Base, check it with Plexa and get me an executable quote for $500."

The agent calls plexa_pretrade_check (verdict + reasons) and plexa_quote (executable price under $500), pays $0.05 + $0.02 in USDC automatically, and answers with real on-chain economics.

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Notes

• Client-only. Talks to the public Plexa API over HTTPS. No service internals ship in this package.
• Honest failures. A non-2xx response or a network error becomes a loud tool error — never a clean-looking empty result. An agent can always tell a failure from a pass.
• Built on the official @modelcontextprotocol/sdk + x402.

License

MIT — see LICENSE.

Questions: support@getplexa.com · getplexa.com

Informational on-chain data and heuristic economic signals, not financial advice. Absence of flags is not a guarantee of safety. Verify independently before trading.