🛡️ @aegis-kernel/mcp

Model Context Protocol (MCP) JSON-RPC 2.0 Safety Clearance Middleware
Tool Schema Pinning • Rug-Pull Detection • In-Process Deterministic Pre-Execution Clearance

🚀 Overview

@aegis-kernel/mcp provides native safety clearance middleware for Model Context Protocol (MCP) servers and clients. It intercepts JSON-RPC 2.0 tools/call requests, verifies schema stability (preventing tool poisoning and rug-pull attacks), and validates argument invariants in sub-1.5ms.

Key Capabilities:

• Zero-Latency Invariant Clearance: Validates SQL ASTs, numeric ranges, and PII patterns on tool arguments.
• MCP Schema Pinning: Computes cryptographic SHA-256 hashes of tool schemas upon initialization to detect runtime drift or malicious schema replacement.
• Output Sanitization: Automatically scans and masks leaked secrets and PII from tool outputs before returning results to the LLM.
• Confused-Deputy Defense: Propagates caller identity tokens to ensure tenant-isolated tool access.

📦 Installation

npm install @aegis-kernel/mcp @aegis-kernel/core

⚡ Quickstart

import { AegisMCPMiddleware } from '@aegis-kernel/mcp';

// 1. Initialize MCP Middleware with policy packs
const middleware = new AegisMCPMiddleware({
  mode: 'enforce',
  packs: ['@aegis/sql-guard', '@aegis/data-guard', '@aegis/finance-guard'],
  enableSchemaPinning: true,
  sanitizeOutputs: true,
});

// 2. Wrap an MCP Server Tool Handler
const safeExecuteSqlHandler = middleware.wrapToolHandler(
  {
    name: 'execute_sql',
    description: 'Executes a database query safely',
    inputSchema: {
      type: 'object',
      properties: { query: { type: 'string' } },
      required: ['query'],
    },
  },
  async (args) => {
    // This handler will ONLY execute if arguments pass deterministic invariants
    return await db.query(args.query);
  }
);

📄 License

Distributed under the MIT License. Copyright (c) 2026 Sneh Gabani.