MCP Orchestrator

A central hub that connects to multiple downstream MCP servers, aggregates their tools, and provides unified access with powerful tool search capabilities.

Built around deferred tool loading — search across all your servers without blowing Claude's context window.

Features

• Config-based Server Registration: Add downstream MCP servers via JSON config file
• Tool Namespacing: Automatic server_name__tool_name format
• Tool Search: Unified BM25/regex search with deferred loading support
• Flexible Authentication: Static saved headers or token forwarding
• Multiple Transports: stdio or HTTP
• Tool Definition Caching: Cached definitions, raw result passthrough
• Storage Backends: In-memory (development) or Redis (production)

Quick Start

Installation

pip install mcp-orchestrator

Running the MCP Server

# Run as stdio MCP server (for Claude Desktop, Cursor, etc.)
mcp-orchestrator

# Or run with Python directly
python -m mcp_orchestrator.main

HTTP Transport:

ORCHESTRATOR_TRANSPORT=http ORCHESTRATOR_PORT=8080 python -m mcp_orchestrator.main

This starts the server on http://localhost:8080/mcp with CORS enabled.

Configuring Servers

Add downstream MCP servers in server_config.json:

{
  "servers": [
    {
      "name": "my-server",
      "url": "http://localhost:8080/mcp",
      "transport": "http",
      "auth_type": "static",
      "auth_headers": {
        "Authorization": "Bearer my-token"
      }
    },
    {
      "name": "my-stdio-server",
      "url": "server.py",
      "transport": "stdio",
      "command": "uv",
      "args": ["run", "python", "server.py"]
    }
  ]
}

Searching for Tools

The orchestrator provides unified tool search (BM25 by default, regex optional):

# BM25 search (default - natural language)
results = await mcp_client.call_tool("tool_search", {
    "query": "get weather information",
    "max_results": 3
})

# Regex search (set use_regex=true)
results = await mcp_client.call_tool("tool_search", {
    "query": "weather|forecast",
    "use_regex": true,
    "max_results": 3
})

Architecture

┌─────────────────────────────────────────────────────┐
│                  MCP Orchestrator                    │
│                                                      │
│  ┌──────────────────────────────────────────────┐   │
│  │              FastMCP Server                   │   │
│  │  ┌─────────────┐  ┌──────────────────┐   │   │
│  │  │ tool_search │  │ call_remote_tool  │   │   │
│  │  └─────────────┘  └──────────────────┘   │   │
│  └──────────────────────────────────────────────┘   │
│                                                      │
│  ┌──────────┐  ┌──────────┐  ┌──────────────┐      │
│  │  Server  │  │   Tool   │  │   Storage    │      │
│  │ Registry │  │  Search  │  │(Memory/Redis)│      │
│  └──────────┘  └──────────┘  └──────────────┘      │
└─────────────────────────────────────────────────────┘
                           │
        ┌───────────────────┼───────────────────┐
        ▼                   ▼                   ▼
   ┌─────────┐        ┌─────────┐        ┌─────────┐
   │ MCP Svr │        │ MCP Svr │        │ MCP Svr │
   │   #1    │        │   #2    │        │   #N    │
   └─────────┘        └─────────┘        └─────────┘

Configuration

Environment Variables

Variable	Default	Description
STORAGE_BACKEND	memory	Storage backend (memory or redis)
REDIS_URL	redis://localhost:6379/0	Redis connection URL
MCP_ORCHESTRATOR_TOOL_CACHE_TTL	300	Tool schema cache TTL in seconds
MCP_ORCHESTRATOR_DEFAULT_CONNECTION_MODE	stateless	Default connection mode
MCP_ORCHESTRATOR_CONNECTION_TIMEOUT	30.0	Connection timeout in seconds
MCP_ORCHESTRATOR_MAX_RETRIES	3	Maximum retry attempts
ORCHESTRATOR_TRANSPORT	stdio	MCP transport (stdio or http)
ORCHESTRATOR_PORT	8080	Port for HTTP transport
ORCHESTRATOR_HOST	0.0.0.0	Host for HTTP transport
ORCHESTRATOR_LOG_LEVEL	INFO	Logging level
SERVER_CONFIG_PATH	server_config.json	Path to server configuration file

Claude Desktop Integration

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "mcp-orchestrator": {
      "command": "mcp-orchestrator",
      "env": {
        "STORAGE_BACKEND": "memory",
        "ORCHESTRATOR_LOG_LEVEL": "INFO"
      }
    }
  }
}

MCP Tools

tool_search

Search for tools using BM25 relevance ranking or regex pattern matching.

@mcp.tool()
async def tool_search(
    query: str,
    max_results: int = 3,
    use_regex: bool = False,
) -> dict:
    """Search for tools using BM25 or regex.

    By default uses BM25 natural language search. Set use_regex=True
    to search using Python regex patterns instead.
    """

discover_tools

Discover tools from a registered downstream server.

@mcp.tool()
async def discover_tools(
    server_name: str,
) -> dict:
    """Discover tools from a registered server and index them for search.

    Returns the list of discovered tools with their schemas.
    """

call_remote_tool

Call a tool directly on a downstream MCP server.

@mcp.tool()
async def call_remote_tool(
    tool_name: str,
    arguments: Optional[dict] = None,
    auth_header: Optional[str] = None,
) -> Any:
    """Call a tool on a downstream server.

    Args:
        tool_name: Namespaced tool name (server_name__tool_name)
        arguments: Tool arguments
        auth_header: Optional auth header to override server's configured auth
    """

Tool Search Results

The search tools return results in the format expected by Claude's tool search system:

{
  "success": true,
  "tool_references": [
    {
      "type": "tool_reference",
      "tool_name": "server_name__tool_name"
    }
  ],
  "total_matches": 5,
  "query": "weather"
}

Testing

Run the test suite:

uv run pytest

Run with coverage:

uv run pytest --cov=mcp_orchestrator

Project Structure

mcp-orchestrator/
├── src/mcp_orchestrator/
│   ├── __init__.py
│   ├── main.py              # Entry point
│   ├── models.py            # Pydantic models
│   ├── mcp_server.py        # FastMCP server
│   ├── config_loader.py     # Config file loader
│   ├── server/
│   │   └── registry.py      # Server registry
│   ├── tools/
│   │   ├── router.py       # Tool router
│   │   └── search.py       # Tool search service
│   └── storage/
│       ├── base.py          # Storage interface
│       ├── memory.py        # In-memory backend
│       └── redis.py         # Redis backend
├── tests/
│   ├── test_registry.py
│   ├── test_search.py
│   ├── test_storage.py
│   ├── test_models.py
│   └── test_integration.py
├── server_config.json       # Pre-configured downstream servers
├── pyproject.toml
├── README.md
└── .env                    # Environment variables (not committed)

License

MIT License

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.