mcp-later

One command to make MCP Servers free until they are actually used.

mcp-later is a lightweight proxy that wraps any MCP stdio server. It caches discovery responses (tools/list, prompts/list, etc.) to disk, and doesn't start the real server until it's actually needed (e.g., tools/call).

The problem

Every time you start a Claude Code session, all configured MCP servers are spawned just to list their tools. If you have browser-mcp configured globally, Chrome gets taken over immediately -- even if you never use a browser tool.

The fix

Wrap any MCP server command with mcp-later. Discovery responses are served from a local disk cache, and the real server is only started when a tool is actually invoked.

npm i -g mcp-later

mcp-later is a ~300 line bash script with zero dependencies.

Usage

Claude Code

Change your MCP server config from this:

{
  "mcpServers": {
    "browser-mcp": {
      "command": "npx",
      "args": ["@browsermcp/mcp@latest"]
    }
  }
}

To this:

{
  "mcpServers": {
    "browser-mcp": {
      "command": "mcp-later",
      "args": ["npx", "@browsermcp/mcp@latest"]
    }
  }
}

That's it. Your MCP server's tools show up instantly from cache, and the real server only starts when a tool is called.

Pre-warm the cache

On first run, mcp-later automatically spawns the server to populate the cache. If you want to do this ahead of time:

mcp-later --warmup npx @browsermcp/mcp@latest

How it works

1. Phase 1 (cached): mcp-later responds to initialize, tools/list, prompts/list, and resources/list from disk cache. The real server is never started.

2. Phase 2 (passthrough): When a non-cached request arrives (e.g., tools/call), the real server is spawned, the init handshake is replayed, and mcp-later becomes a transparent bidirectional pipe for the rest of the session.

Cache files are stored in ~/.cache/mcp-later/ and expire after 24 hours by default.

Configuration

All configuration is via environment variables:

| Variable | Default | Description | |---|---|---| | MCP_LATER_CACHE_DIR | ~/.cache/mcp-later | Cache directory | | MCP_LATER_TTL | 86400 (24h) | Cache lifetime in seconds | | MCP_LATER_DEBUG | (unset) | Set to any value to enable debug logging to stderr |

License

MIT