Emceepee

emceepee

Connect to any MCP server, anytime. Access the full MCP protocol through tools.

[](https://www.npmjs.com/package/emceepee) [](https://opensource.org/licenses/MIT)

npx emceepee

Why?

Problem 1: Static connections. Most MCP clients only connect to servers at startup. Want to connect to a new server mid-session? Restart everything.

Problem 2: Incomplete protocol support. MCP has rich features—resources, prompts, notifications, sampling, elicitations—but many clients only implement tools. Those features? Inaccessible.

emceepee solves both. It's a proxy that exposes the entire MCP protocol as tools. Any client that supports tool calling can now:

• Connect to new MCP servers dynamically (HTTP or stdio)
• Spawn and manage MCP server processes with automatic crash recovery
• Access resources and resource templates
• Use prompts
• Receive notifications and logs (with source filtering)
• Handle sampling requests (bidirectional LLM calls)
• Handle elicitations (user input requests)

Quick Start

1. Add to your MCP client

Claude Code / Claude Desktop (.mcp.json):

{
  "mcpServers": {
    "emceepee": {
      "command": "npx",
      "args": ["emceepee"]
    }
  }
}

Other clients — point to the HTTP server:

npx emceepee-http  # runs on http://localhost:8080/mcp

2. Connect to servers mid-session

Ask your LLM:

> "Connect to http://localhost:3001/mcp and show me what it can do"

The LLM will use emceepee's tools to connect, explore, and interact with the server.

---

How It Works

┌────────────┐     ┌───────────┐     ┌──────────────┐
│ MCP Client │────▶│ emceepee  │────▶│ MCP Server 1 │
│            │     │           │     └──────────────┘
│ (tools     │◀────│  (proxy)  │────▶┌──────────────┐
│   only)    │     │           │     │ MCP Server 2 │
└────────────┘     └───────────┘     └──────────────┘

emceepee exposes a static set of tools that never change. These tools provide access to the full MCP protocol, letting any tool-capable client use features it doesn't natively support.

Server Transports

emceepee supports two transport types for connecting to backend MCP servers:

HTTP/SSE Transport

Connect to remote MCP servers over HTTP with Server-Sent Events:

add_server(name: "myserver", url: "http://localhost:3001/mcp")

Stdio Transport (Process Management)

Spawn and manage MCP servers as child processes communicating via stdin/stdout:

add_server(name: "myserver", command: "node", args: ["server.js"])

Stdio features:

• Automatic crash recovery with exponential backoff restart
• Stderr capture for debugging (exposed via get_logs with source: "stderr")
• Lifecycle events for monitoring process state
• Configurable restart behavior (max attempts, delays, backoff multiplier)

Process Lifecycle Events

When using stdio transport, emceepee tracks the full process lifecycle:

| Event | Description | |-------|-------------| | process_started | Process spawned successfully | | process_crashed | Process exited unexpectedly | | restarting | Attempting to restart (with attempt count) | | restarted | Successfully restarted after crash | | restart_failed | Max restart attempts exceeded | | process_stopped | Process stopped cleanly |

Restart Configuration

Customize crash recovery behavior per server:

{
  "restartConfig": {
    "enabled": true,
    "maxAttempts": 5,
    "baseDelayMs": 1000,
    "maxDelayMs": 60000,
    "backoffMultiplier": 2
  }
}

Tools

Server Management

| Tool | Description | |------|-------------| | add_server | Connect to a backend MCP server | | remove_server | Disconnect from a server | | list_servers | List connected servers with status |

Tools

| Tool | Description | |------|-------------| | list_tools | List tools from connected servers (with regex filtering) | | execute_tool | Run a tool on a backend server |

Resources

| Tool | Description | |------|-------------| | list_resources | List available resources | | list_resource_templates | List resource templates | | read_resource | Fetch a resource by URI | | subscribe_resource | Subscribe to resource change notifications | | unsubscribe_resource | Unsubscribe from resource change notifications |

Prompts

| Tool | Description | |------|-------------| | list_prompts | List available prompts | | get_prompt | Get a prompt with arguments |

Notifications & Logs

| Tool | Description | |------|-------------| | get_notifications | Get buffered server notifications | | get_logs | Get buffered log messages with source filtering |

The get_logs tool supports filtering by log source:

• protocol: MCP protocol messages and notifications
• stderr: Process stderr output (for stdio servers)
• stdout: Process stdout capture (for local HTTP servers)

Example: Get only protocol logs by excluding stderr/stdout:

{ "exclude_sources": ["stderr", "stdout"] }

Sampling (bidirectional LLM requests)

| Tool | Description | |------|-------------| | get_sampling_requests | Get pending requests from servers wanting LLM completions | | respond_to_sampling | Send an LLM response back to the server |

Elicitations (user input requests)

| Tool | Description | |------|-------------| | get_elicitations | Get pending requests for user input | | respond_to_elicitation | Send user input back to the server |

Tasks & Activity

| Tool | Description | |------|-------------| | list_tasks | List background tasks | | get_task | Get task status | | cancel_task | Cancel a running task | | await_activity | Wait for server events (polling) |

Timers

| Tool | Description | |------|-------------| | set_timer | Create a timer that fires after a duration | | list_timers | List all timers | | get_timer | Get timer details | | delete_timer | Delete a timer (returns timer body) |

Codemode (Reduced-Context API)

| Tool | Description | |------|-------------| | codemode_search | Search for capabilities across all servers | | codemode_execute | Execute JavaScript with access to mcp.* API |

Codemode API

Codemode is a reduced-context API that exposes just 2 tools instead of the full set. This dramatically reduces token usage when AI needs to perform complex multi-step MCP operations.

Tools

codemode_search - Search for tools, resources, prompts, or servers using regex patterns:

{
  "query": "file|read",
  "type": "tools",
  "server": "myserver",
  "includeSchemas": false
}

codemode_execute - Run JavaScript in a sandboxed environment:

{
  "code": "const tools = await mcp.listTools(); return tools.length;",
  "timeout": 30000
}

The mcp.* API

Inside codemode_execute, your code has access to:

// Server discovery
await mcp.listServers()

// Tool operations
await mcp.listTools(serverPattern?)
await mcp.callTool(server, tool, args?)

// Resource operations
await mcp.listResources(serverPattern?)
await mcp.listResourceTemplates(serverPattern?)
await mcp.readResource(server, uri)

// Prompt operations
await mcp.listPrompts(serverPattern?)
await mcp.getPrompt(server, name, args?)

// Utilities
await mcp.sleep(ms)    // max 5 seconds per call
mcp.log(...args)       // captured in result.logs

Example: Multi-Step Operation

// Find all "search" tools and call the first one
const tools = await mcp.listTools();
const searchTools = tools.filter(t => t.name.includes('search'));

if (searchTools.length === 0) {
  return { error: 'No search tools found' };
}

const tool = searchTools[0];
mcp.log(`Calling ${tool.server}/${tool.name}`);

const result = await mcp.callTool(tool.server, tool.name, {
  query: 'example'
});

return {
  tool: tool.name,
  server: tool.server,
  result: result.content
};

Security Features

• Sandboxed execution - Blocked globals: process, require, eval, fetch, setTimeout, Function, etc.
• Timeout enforcement - 1 second to 5 minutes (default 30s)
• MCP call limits - Maximum 100 mcp.* calls per execution
• Code size limits - Maximum 100KB of code

Configuration

Codemode is enabled by default. To disable:

CLI flag:

npx emceepee --no-codemode
npx emceepee-http --no-codemode

Environment variable:

EMCEEPEE_NO_CODEMODE=1 npx emceepee

Library usage:

registerTools(server, sessionManager, sessions, requestTracker, {
  codemodeEnabled: false
});

Context Info

Every tool response may include additional context information as a second JSON text block. This provides real-time status without requiring explicit polling:

{
  "content": [
    { "type": "text", "text": "Tool result here" },
    { "type": "text", "text": "{\"pending_client\":{\"sampling\":1,\"elicitation\":0},\"expired_timers\":[{\"id\":\"...\",\"message\":\"Check status\",\"expiredAt\":\"...\"}],\"notifications\":[...]}" }
  ]
}

Context info fields:

| Field | Description | |-------|-------------| | pending_client.sampling | Number of pending sampling requests (urgent - servers are blocked) | | pending_client.elicitation | Number of pending elicitation requests (urgent - servers are blocked) | | expired_timers | Timers that have fired since the last tool call (cleared after delivery) | | notifications | Buffered notifications from backend servers (cleared after delivery) |

Context info is only included when there's something to report.

Installation

# Run directly
npx emceepee

# Or install globally
npm install -g emceepee

Usage

stdio transport (Claude Code, Claude Desktop)

npx emceepee

HTTP transport (web clients, custom integrations)

# Default port 8080
npx emceepee-http

# Custom port
PORT=9000 npx emceepee-http

# With pre-configured servers
npx emceepee-http --config servers.json

Configuration File

Pre-configure backend servers (HTTP and stdio):

{
  "servers": [
    {
      "name": "remote-server",
      "url": "http://localhost:3001/mcp"
    },
    {
      "name": "local-server",
      "type": "stdio",
      "command": "node",
      "args": ["./my-mcp-server.js"],
      "env": { "DEBUG": "true" },
      "restartConfig": {
        "maxAttempts": 3,
        "baseDelayMs": 1000
      }
    }
  ]
}

Example Session

User: Connect to http://localhost:3001/mcp as "gameserver"

LLM: [uses add_server]
Connected to gameserver successfully.

User: What can it do?

LLM: [uses list_tools, list_resources, list_prompts]
gameserver has:
- 3 tools: screenshot, send_chat, move
- 2 resources: player_state, world_info
- 1 prompt: describe_scene

User: Get the player state

LLM: [uses read_resource with uri="minecraft://state"]
Player is at position (100, 64, -200), health: 18/20

Library Usage

emceepee can also be used as a library for building custom MCP integrations:

MCPStdioClient

Spawn and manage MCP servers as child processes:

import { MCPStdioClient } from "emceepee";

const client = new MCPStdioClient({
  name: "my-server",
  command: "node",
  args: ["server.js"],
  restartConfig: {
    maxAttempts: 5,
    baseDelayMs: 1000,
  },
  onLifecycleEvent: (event) => {
    console.log(`${event.event}: ${JSON.stringify(event)}`);
  },
  onLog: (log) => {
    if (log.source === "stderr") {
      console.error(`[stderr] ${log.data}`);
    }
  },
});

await client.connect();

// Use the client
const tools = await client.listTools();
const result = await client.callTool("my-tool", { arg: "value" });

// Clean shutdown
await client.disconnect();

IMCPClient Interface

Both HTTP and stdio clients implement the common IMCPClient interface:

import { IMCPClient, isStdioClient, isHttpClient } from "emceepee";

function handleClient(client: IMCPClient) {
  if (isStdioClient(client)) {
    // Stdio-specific operations (e.g., access stderr buffer)
  } else if (isHttpClient(client)) {
    // HTTP-specific operations
  }

  // Common operations work on both
  const tools = await client.listTools();
  const info = client.getInfo();
}

Development

bun install              # Install dependencies
bun run dev              # stdio server (development)
bun run dev:http         # HTTP server (development)
bun run check            # TypeScript + ESLint
bun run test             # Run tests
bun run build            # Production build

Testing

bun run test             # Run all tests
bun run test:stdio       # Run stdio client tests
bun run test:codemode    # Run codemode tests

Tests cover:

• Stdio client: Connection lifecycle, tool invocation, stderr capture, crash recovery, lifecycle events
• Codemode: Sandbox isolation, timeout enforcement, API bindings, search/execute functionality, error handling

License

MIT © Andrew Jefferson

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: eastlondoner
• Source: eastlondoner/emceepee
• License: MIT
• Homepage: https://github.com/eastlondoner/emceepee

Install and usage instructions live in the source repository linked above.