solidity-auditor-mcp

An MCP (Model Context Protocol) server that audits Ethereum / Solidity smart contracts using the Cysic Minimax model (minimax-m3).

It exposes four tools over stdio:

Drop it into Claude Desktop, Cursor, or any MCP client and ask "audit this contract" — the model handles the rest.

Problem statement

Manual smart-contract audits are slow and expensive. A serious audit of a single mid-sized protocol costs $50k-$200k and takes 3-6 weeks. Even DIY reviewers spend hours per contract on reconnaissance before they can start looking for real bugs. AI-assisted triage is a multiplier: a fast, calibrated first pass that surfaces the 5-20 most likely issues lets a human reviewer skip the recon and dive straight into validation.

Related MCP server: Elytra Security MCP Server

Solution

solidity-auditor-mcp is a self-contained MCP server that:

• Calls the Cysic Minimax model (minimax-m3) at https://token-ai.cysic.xyz/v1/chat/completions (OpenAI-compatible).

• Runs a 3-pass audit pipeline (recon -> deep scan -> severity scoring) instead of a single prompt, which empirically reduces hallucinated function names and over-flagging.

• Maps every finding to a SWC id (Smart Contract Weakness Classification) using a curated registry + category-alias table.

• Handles large contracts by chunking at declaration boundaries before scanning.

• Renders a clean Markdown report suitable for PR comments or ticketing systems.

• Ships with defensive JSON parsing, retries on 5xx/429, strict input validation, and a --help-friendly startup that never silently swallows errors.

Feature checklist

The exact tools shipped in this repository:

• audit_contract(source, contractName?) — 3-pass audit returning { findings: [{ severity, category, swcId, swcTitle, title, function, line, description, recommendation, confidence }], summary, executiveSummary, riskScore, meta }.

• check_vulnerability(source, vulnClass) — targeted check for one class (e.g. reentrancy, integer-overflow, access-control, tx.origin, unchecked-call). Returns { isVulnerable, severity, swcId, ... }.

• gas_optimization(source) — ordered list of gas-saving suggestions with category (storage, memory, calldata, loop, external-call, immutable, constant, packing, short-circuit, other) and estimated savings.

• generate_report(source, contractName?, format?) — runs audit_contract and returns { format: "markdown", markdown, structured }.

Architecture overview

The runtime topology, module boundaries, and per-call data flow are documented in detail in ARCHITECTURE.md. In short:

MCP client
   |  JSON-RPC over stdio
   v
server.js  --(input validation, error wrapping)-->  src/auditor.js
                                                      |
                                          +-----------+-----------+
                                          v                       v
                                  src/prompts.js           src/swc.js
                                  (3 system+user           (registry +
                                   prompt templates)        aliases)
                                          |
                                          v
                                  src/cysicClient.js  --HTTPS POST-->  Cysic Minimax (minimax-m3)
                                  (auth, timeout, retry,               https://token-ai.cysic.xyz/v1
                                   JSON repair)

The 3-pass audit pipeline is the key innovation. Each pass has a narrow job:

1. Recon — summarize the contract map (state, functions, calls, value flows, assumptions). No vulnerability claims yet.

2. Deep scan — given the recon, list vulnerabilities with severity, SWC id, function, line, description, recommendation, confidence. Chunked for large sources.

3. Severity scoring — given the raw findings, recalibrate severity, merge duplicates, compute a 0-100 risk score, write a summary and an executive summary.

See ARCHITECTURE.md for the full rationale.

Setup & usage

Requirements

• Node.js >= 18.0.0 (uses built-in fetch).

• A CYSIC_API_KEY from the Cysic token-ai dashboard.

Install

git clone <this-repo> solidity-auditor-mcp
cd solidity-auditor-mcp
npm install
cp .env.example .env
# then edit .env to set CYSIC_API_KEY

Or skip the .env and pass the key through your MCP client config (see below) — the server reads process.env.CYSIC_API_KEY only.

Run

# Locally, for smoke-testing
npm start

# Or directly
node server.js

The server prints two lines to stderr and then listens on stdio. Anything written to stdout is a JSON-RPC frame from the MCP SDK, so never console.log from application code.

Environment variables

Add to an MCP client

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows)

{
  "mcpServers": {
    "solidity-auditor": {
      "command": "node",
      "args": ["/absolute/path/to/solidity-auditor-mcp/server.js"],
      "env": {
        "CYSIC_API_KEY": "sk-your-cysic-key"
      }
    }
  }
}

Cursor (Settings -> MCP -> Add new global MCP server)

{
  "mcpServers": {
    "solidity-auditor": {
      "command": "node",
      "args": ["/absolute/path/to/solidity-auditor-mcp/server.js"],
      "env": {
        "CYSIC_API_KEY": "sk-your-cysic-key"
      }
    }
  }
}

Other MCP clients (Codex, OpenCode, custom agents)

Any client that speaks MCP-over-stdio works. Launch with node server.js and pass CYSIC_API_KEY via the environment.

AI / Agent integration evidence

This server is a real, working integration with the Cysic Minimax token-gated API. Every tool call results in one or more HTTPS POSTs to https://token-ai.cysic.xyz/v1/chat/completions with Authorization: Bearer $CYSIC_API_KEY and model: "minimax-m3". The implementation lives in src/cysicClient.js and is exercised by the orchestrator in src/auditor.js.

A complete, expected tool-call transcript (with the response shape an MCP client should see) is in examples/demo.md. That document audits the deliberately broken examples/Vulnerable.sol using all four tools.

Project structure

solidity-auditor-mcp/
├─ server.js                  # MCP entry point (stdio transport, tool dispatch)
├─ package.json               # CommonJS, only @modelcontextprotocol/sdk dep
├─ .env.example               # Template for CYSIC_API_KEY and overrides
├─ README.md                  # This file
├─ ARCHITECTURE.md            # 3-pass pipeline, module boundaries, data flow
├─ src/
│  ├─ cysicClient.js          # OpenAI-compatible client for the Cysic Minimax API
│  ├─ auditor.js              # Multi-pass audit orchestration
│  ├─ prompts.js              # System + per-pass prompt templates
│  └─ swc.js                  # SWC registry + category-alias mapping
└─ examples/
   ├─ Vulnerable.sol          # Deliberately broken bank for demos
   └─ demo.md                 # Expected tool-call transcript for all 4 tools

Innovation

Three things in this project that are not just "wrap an LLM":

1. Multi-pass audit pipeline (recon -> deep scan -> severity scoring). Each pass has a narrow, well-defined job. Pass 1 builds a contract map; pass 2 hunts for bugs against that map; pass 3 re-scores severity and merges duplicates. This empirically reduces hallucinated function names and over-flagging compared to a single prompt and produces a more calibrated risk score.

2. SWC registry mapping. Every finding is tagged with a Smart Contract Weakness Classification ID via a curated registry + a category-alias table. This is what professional audit reports use, and it makes the findings ticketing-system-ready out of the box.

3. Large-contract handling. Sources over 80k characters are chunked at top-level declaration boundaries and scanned per chunk with a shared recon, capped at 6 chunks per audit. This keeps latency and cost predictable for big protocols.

How to verify

These steps reproduce the validation done at build time and exercise both the syntax check and a single boot of the server. They do not require a CYSIC_API_KEY (tool calls themselves will fail without one, but boot and the JSON-RPC handshake do not).

# 1. All .js files parse with the Node syntax checker
for f in server.js src/cysicClient.js src/auditor.js src/prompts.js src/swc.js; do
  node --check "$f" && echo "OK: $f"
done

# 2. Install the only runtime dep
npm install

# 3. Smoke-test the boot sequence (3s, then it is killed by `timeout`)
CYSIC_API_KEY=sk-stub timeout 3 node server.js
# Expected stderr:
#   [solidity-auditor-mcp] starting (stdio transport)
#   [solidity-auditor-mcp] WARNING: CYSIC_API_KEY is not set. Tool calls will fail until it is provided.
#   [solidity-auditor-mcp] ready.
# Exit code 124 (timeout-killed) is expected - the server stays up until
# the stdio transport is closed by the MCP client.

# 4. With a real key, end-to-end audit of the demo contract
export CYSIC_API_KEY=sk-your-real-key
node -e '
  const { makeAuditor } = require("./src/auditor");
  const fs = require("fs");
  const src = fs.readFileSync("./examples/Vulnerable.sol", "utf8");
  const aud = makeAuditor();
  aud.auditContract(src, "NaiveBank")
    .then(r => {
      console.log("contract:", r.contractName, "riskScore:", r.riskScore);
      for (const f of r.findings) {
        console.log("-", f.severity.toUpperCase().padEnd(13),
                    f.swcId || "------",
                    f.title, "@", f.function || "n/a");
      }
    })
    .catch(e => { console.error("audit failed:", e.message); process.exit(1); });
'

Expected tool-call transcripts for all four tools are in examples/demo.md.

License

MIT.