dynmcp

Dynamic Discovery MCP

A proxy MCP that exposes meta-tools so agents can discover and call upstream MCP tools on demand, without loading every tool schema into the context window.

Full documentation: dynamicmcp.tools

Features

• Two meta-tools instead of N. Wraps one or more upstream MCPs and exposes only discover_tool and use_tool to the agent. Full schemas of irrelevant tools never enter context.
• Dynamic discovery of whole MCPs. Mark MCPs with a description in your config and they stay disconnected until the agent calls load_mcp — deferring entire MCP catalogs out of context until they are actually needed.
• Full-fidelity proxying. Resources, prompts, completion, logging, notifications, cancellation, progress, and server-initiated requests (sampling, elicitation, roots) pass through unchanged.
• Multiple transports for upstreams. stdio child processes, streamable-http, and sse — all in one config.
• JSON or YAML config with shell-style ${VAR} and ${VAR:-default} environment variable interpolation.
• Local-only. Single Node.js process speaking MCP over stdio. No daemon, no remote endpoint.

Getting Started

Wrap a single upstream MCP

# Before — tool schemas go straight into context
npx -y chrome-devtools-mcp@latest

# With dynmcp — only discover_tool and use_tool are exposed
npx dynmcp@latest -- npx -y chrome-devtools-mcp@latest

Everything after -- is the command used to launch the upstream MCP. In this mode tool names are exposed as-is (no namespace prefix).

Proxy multiple MCPs from a config file

Create a mcp.json in your project root:

{
  "$schema": "https://dynamicmcp.tools/config.json",
  "mcp": {
    "chrome-devtools": {
      "transport": "stdio",
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest"]
    },
    "filesystem": {
      "transport": "stdio",
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
    }
  }
}

Then run:

# Auto-discover mcp.json or .mcp.json
npx dynmcp@latest

# Or specify explicitly
npx dynmcp@latest --config ./my-config.json

In config-file mode tool names are namespaced as <mcp-name>/<tool-name> to avoid collisions.

Dynamic Discovery

For configs with heavier MCPs you only sometimes need (Chrome DevTools, remote APIs, anything expensive to keep open), give the entry a description. That MCP becomes lazy: dynmcp doesn't open the connection at startup, and the agent only sees a short summary of what the MCP does. When the agent decides it actually needs that MCP, it calls load_mcp with the server's name and the connection opens on demand.

{
  "$schema": "https://dynamicmcp.tools/config.json",
  "mcp": {
    "filesystem": {
      "transport": "stdio",
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
    },
    "chrome-devtools": {
      "description": "Chrome browser automation and DevTools control. Navigate pages, take screenshots, inspect the DOM, run JavaScript. Use when you need to interact with or debug a live web page.",
      "transport": "stdio",
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest"]
    }
  }
}

filesystem connects at startup. chrome-devtools stays lazy until the agent loads it. Once loaded, it behaves exactly like an eager MCP for the rest of the session.

See the Dynamic Discovery guide for the capability caveat, the retry budget, and tips on writing descriptions agents can act on.

Full docs cover environment variable interpolation, all transport options, and the complete CLI reference.