gtwmcp — MCP Gateway

A zero-dependency MCP gateway. Connect multiple AI harnesses to multiple MCP servers through a single, centrally-managed stdio interface. No overhead, no bloat — just the Node.js stdlib. Secrets stay in the OS keychain, never in config files.

Install

npm install -g gtwmcp

Requires Node.js >= 22.

Quick Start

Add a stdio MCP server:

$ gtwmcp add github --type stdio --command npx --args "-y,@modelcontextprotocol/server-github" --description "GitHub MCP"
Server "github" added.

Add an SSE MCP server with OAuth:

$ gtwmcp add jira --type sse --url https://mcp.jira.example.com/sse --oauth --description "Jira MCP"
Server "jira" added.

List servers:

$ gtwmcp list
NAME    TYPE   STATUS       DESCRIPTION
------  -----  -----------  -----------
github  stdio  ✅ enabled   GitHub MCP
jira    sse    ✅ enabled   Jira MCP

Authenticate an OAuth server:

$ gtwmcp auth jira
[jira] https://mcp.jira.example.com/sse
  ✅ Token valid (expires in 45m)

$ gtwmcp auth --force          # re-authenticate all OAuth servers

List tools from a server:

$ gtwmcp get jira
jira (sse) — https://mcp.jira.example.com/sse
Listing tools...

  1. search_jira_issues: Search Jira issues using JQL
  2. get_jira_issue: Get a specific Jira issue

2 tools available.

CLI Reference

gtwmcp add    <name>    Add or update an MCP server
gtwmcp remove <name>    Remove an MCP server
gtwmcp get    <name>    List tools and descriptions from a server
gtwmcp list             List all servers with status
gtwmcp auth   [name]    Authenticate OAuth servers (--force to re-auth)
gtwmcp enable <name>    Enable a server
gtwmcp disable <name>   Disable a server
gtwmcp serve            Start the MCP gateway in stdio mode

Gateway

The gateway (gtwmcp serve) speaks MCP over stdio to the client. On startup it:

1. Reads ~/.gtwmcp.json
2. Connects to all enabled upstream servers in parallel
3. Calls initialize and tools/list on each
4. Prefixes every tool with the server name: <server>__<tool>
5. Applies allow/block list filters
6. Presents a single consolidated tool list

Tool Filtering

Control which tools are exposed via environment variables:

Variable	Behavior
GTWMCP_ALLOW_LIST	Only matching tools pass
GTWMCP_BLOCK_LIST	All tools except matching pass
Both set	Allow first, then block removes from that subset
Neither set	All tools pass

Patterns support trailing * wildcard:

# Expose only read tools
GTWMCP_ALLOW_LIST="github__read_*,github__search_*,github__list_*"

# Expose everything except destructive tools
GTWMCP_BLOCK_LIST="github__delete_*,github__admin_*"

Configuration

~/.gtwmcp.json:

{
  "version": 1,
  "servers": {
    "github": {
      "type": "stdio",
      "enabled": true,
      "description": "GitHub MCP server",
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_xxxxxxxxxxxx"
      }
    },
    "jira": {
      "type": "sse",
      "enabled": true,
      "description": "Jira MCP",
      "url": "https://mcp.jira.example.com/sse",
      "headers": {
        "X-Custom-Header": "value"
      },
      "oauth": true
    }
  }
}

• stdio: command, args, optional env and description
• sse: url, optional headers, oauth, and description
• "oauth": true means all OAuth data lives in the OS keychain (never in this file)

OAuth

The gateway supports Authorization Code Flow with PKCE for SSE servers.

At runtime, gtwmcp serve auto-refreshes expired tokens before each call.

Keychain

Platform	Backend
macOS	/usr/bin/security (Keychain)
Linux	secret-tool (libsecret)

Use with Claude Code

Point Claude Code's MCP config at the gateway:

{
  "mcpServers": {
    "gtwmcp": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "gtwmcp", "serve"]
    }
  }
}

All your upstream MCP tools appear prefixed and unified in Claude Code.

Development

npm install
npm run check   # syntax validation
npm test        # 57 tests

Zero external dependencies. Node.js 22+ stdlib only.