MCP Hub

MCP Hub

    

MCP Hub is a TypeScript gateway for Model Context Protocol servers. It lets you register multiple downstream MCP servers and expose one hub surface for tool discovery, routing, smart search, and recommendations.

Status: experimental. The project is suitable for local development and portfolio review, but the public API should be treated as pre-1.0.

What It Does

• Aggregates tool metadata across registered MCP servers.
• Routes tool calls to the selected downstream server.
• Provides hub-native tools for catalog browsing, delegated calls, natural-language search, and recommendations.
• Supports stdio and HTTP/SSE downstream server entries.
• Keeps downstream credentials outside the repository through environment variables or per-server env files.
• Includes unit, integration, e2e, performance, and registry hardening tests.

MCP Hub does not bundle third-party MCP servers. All server examples are placeholders that you replace with your own commands, URLs, and credential storage.

Requirements

• Node.js 18 or newer
• npm 10 or newer
• One or more MCP servers that you can run locally or reach over HTTP/SSE

Install

git clone https://github.com/ftaricano/mcp-hub.git
cd mcp-hub
npm ci
npm run build

When an npm package is published, the intended package name is @ftaricano/mcp-hub.

Quickstart

Create a local hub config:

cp hub-config.example.json hub-config.json

Edit hub-config.json so each server entry points to a real MCP server in your environment. Keep hub-config.json local; it is ignored by Git because it may contain paths or environment references that are specific to your machine.

Minimal stdio server example:

{
  "servers": [
    {
      "id": "docs-server",
      "name": "Documentation MCP Server",
      "command": "node",
      "args": ["/absolute/path/to/docs-mcp/dist/index.js"],
      "envFile": "/absolute/path/to/docs-mcp/.env",
      "inheritEnv": ["DOCS_REGION"],
      "protocol": "stdio",
      "enabled": true,
      "timeout": 30000,
      "retries": 2,
      "toolCallRetries": {
        "enabled": true,
        "maxAttempts": 2,
        "retryableTools": ["search_docs"]
      },
      "tags": ["docs", "knowledge"]
    }
  ],
  "cache": {
    "enabled": true,
    "ttl": 300000
  },
  "security": {
    "rate_limit": 100,
    "validate_schemas": true
  },
  "logging": {
    "level": "info",
    "format": "json"
  }
}

Run the hub:

HUB_CONFIG="$PWD/hub-config.json" npm start

MCP Client Config

Register the built hub in any MCP client that supports stdio servers:

{
  "mcpServers": {
    "hub": {
      "command": "node",
      "args": ["/absolute/path/to/mcp-hub/dist/index.js"],
      "env": {
        "HUB_CONFIG": "/absolute/path/to/mcp-hub/hub-config.json"
      }
    }
  }
}

See LMStudio-MCP-Config.md for an LM Studio example.

Hub Tools

MCP Hub exposes four hub-native tools:

• list-all-tools: returns the aggregated downstream tool catalog.
• call-tool: calls a named tool on a named downstream server.
• smart-search: ranks available tools for a natural-language query.
• get-recommendations: returns recommendation-oriented results based on available tool metadata.

Configuration

HUB_CONFIG can point to any JSON file matching the hub config shape. If it is not set, the hub tries common local paths for hub-config.json.

Server entries can use:

• command and args for stdio MCP servers,
• url and protocol: "http" for HTTP/SSE entries,
• env for non-secret static values,
• envFile for per-server secrets or local credentials,
• inheritEnv for explicit parent environment pass-through,
• toolCallRetries for known-idempotent tools only.

Downstream stdio servers inherit only a small runtime-safe environment baseline by default. Add any required parent variables explicitly with inheritEnv.

Architecture

flowchart LR
  Client["MCP client"] --> Hub["MCP Hub"]
  Hub --> Registry["Server registry"]
  Hub --> Search["Smart search and recommendations"]
  Registry --> ServerA["Docs MCP server"]
  Registry --> ServerB["Issue tracker MCP server"]
  Registry --> ServerC["Any other MCP server"]

Key modules:

• src/index.ts: MCP server entry point and hub-native tool handlers.
• src/registry/: downstream server lifecycle, connections, and tool discovery.
• src/intelligence/: search and recommendation scoring.
• src/cache/: result and metadata caching.
• src/utils/redaction.ts: argument summarization without logging raw sensitive values.

Development

npm run type-check
npm run lint
npm run format:check
npm test
npm run build

Useful focused suites:

npm run test:unit
npm run test:integration
npm run test:e2e
npm run test:performance

Packaging

Validate the npm package contents before publishing:

npm pack --dry-run --json

The package is intentionally restricted with the files field in package.json; local configs, logs, tests, coverage, testing-interface/, and generated artifacts should not ship in the npm tarball.

Security

Do not commit secrets or local operational state. In particular, keep these files and directories out of Git:

• .env, .env.* except .env.example
• hub-config.json and machine-specific config variants
• tokens/, auth-state/, config/auth-state/
• credentials.json, token.json, private keys, certificates, logs, and JSONL traces

Report vulnerabilities privately through GitHub Security Advisories. See SECURITY.md for the full policy.

Troubleshooting

If the hub starts but downstream tools do not appear:

• confirm HUB_CONFIG points to the intended file,
• verify each downstream server command, args, url, and protocol,
• run the downstream MCP server directly before registering it behind the hub,
• check whether the server requires variables in envFile or inheritEnv,
• keep mutating tool calls out of retry lists unless they are explicitly idempotent.

If build or tests fail after dependency changes:

• run npm ci from a clean checkout,
• run npm run type-check before debugging runtime behavior,
• remove stale dist/ output with npm run clean && npm run build.

Contributing

Issues and focused pull requests are welcome. Before opening a PR, run:

npm run type-check
npm run lint
npm run format:check
npm test
npm run build

Please avoid committing local credentials, generated logs, screenshots, or machine-specific hub configs.

License

MIT. See LICENSE.