@getcordon/core

Core proxy engine for Cordon for MCP, the security gateway for MCP tool calls.

Most users won't install this directly — it's a dependency of @getcordon/cli. Install this package when you want to embed Cordon programmatically rather than run it via the CLI.

Install

npm install @getcordon/core @getcordon/policy

Programmatic usage

import { CordonGateway } from '@getcordon/core';
import type { ResolvedConfig } from '@getcordon/policy';

const config: ResolvedConfig = {
  servers: [
    {
      name: 'database',
      transport: 'stdio',
      command: 'npx',
      args: ['-y', '@modelcontextprotocol/server-postgres', process.env.POSTGRES_URL!],
      policy: 'read-only',
    },
  ],
  audit: { enabled: true, output: 'stdout' },
  approvals: { channel: 'terminal' },
};

const gateway = new CordonGateway(config);
await gateway.start();
// ... on shutdown:
await gateway.stop();

What's included

• UpstreamManager — manages child-process MCP servers, aggregates their tool registries, filters unknown tools against per-server knownTools catalogs
• PolicyEngine — evaluates policies per tool call (allow / block / approve / approve-writes / read-only / log-only / hidden / sql-read-only / sql-approve-writes); evaluate(server, tool, args?) accepts optional call arguments for SQL-aware policies; includes tool-name write-detection heuristic for read-only and approve-writes; isHidden() query for the gateway's tools/list filter
• classifySql (from ./policies/sql-classifier) — pure helper that parses a SQL string (PostgreSQL dialect) and classifies it as read / write / unknown. Fail-closed on parse error. Exportable for use outside the policy engine.
• Interceptor — the hot path; every tool call flows through policy check + rate limit + audit log
• ApprovalManager — routes approvals to terminal or Slack channels
• AuditLogger — structured JSON logging to stdout, file, or hosted endpoint
• RateLimiter — sliding-window counters at global, per-server, and per-tool granularities

Full documentation

Architecture overview, policy reference, approval flow, and audit format: https://github.com/marras0914/cordon

License

MIT