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milkymap

semantic-mcp

by milkymap

Semantic MCP

PyPI version Docker

Semantic router for MCP ecosystems - Discover, manage, and execute tools across multiple MCP servers with progressive disclosure.

Overview

semantic-mcp is a FastMCP-based MCP server that provides semantic discovery and lifecycle management for other MCP servers. It connects to a discovery service for semantic search and manages server lifecycles locally via ZMQ-based IPC.

LLM Client (Claude/Cline)
    │ MCP Protocol
    ▼
┌─────────────────────────────┐
│       semantic-mcp          │
│    (FastMCP MCP Server)     │
├─────────────────────────────┤
│  Discovery → mcp-index API  │
│  Execution → ZMQ + Sessions │
└─────────────────────────────┘
    │               │
    ▼               ▼
mcp-index       MCP Servers
(Elasticsearch) (stdio/http)

Related MCP server: one-mcp

  • mcp-index - Elasticsearch-based semantic discovery service for MCP servers. Required backend for semantic-mcp to enable semantic search and server registry.

Installation

uvx semantic-mcp serve --transport stdio

Option 2: pip/uv

# Install from PyPI
pip install semantic-mcp

# Or with uv
uv pip install semantic-mcp

# Run
semantic-mcp serve --transport stdio

Option 3: Docker

docker pull milkymap/semantic-mcp:0.2

docker run -d \
  -p 8001:8001 \
  -e DISCOVERY_URL=http://your-discovery-service \
  -e DISCOVERY_API_KEY=your-key \
  milkymap/semantic-mcp:0.2 serve --transport streamable-http --port 8001

Option 4: From source

git clone https://github.com/milkymap/semantic-mcp
cd semantic-mcp
uv sync
uv run semantic-mcp serve

Configuration

Environment Variables

Variable

Description

Default

DISCOVERY_URL

Discovery service API URL

http://localhost:8000

DISCOVERY_API_KEY

API key for discovery authentication

None

DISCOVERY_ENCRYPTION_KEY

Key to decrypt sensitive env vars in server configs

None

TOOL_OFFLOADED_DATA_PATH

Path for large result offloading

/tmp/mcp_offloaded

MAX_RESULT_TOKENS

Max tokens before content offloading

4096

BACKGROUND_QUEUE_SIZE

Max background tasks in queue

100

OPENAI_API_KEY

OpenAI API key (for image descriptions)

None

MCP Client Integration

Claude Code / Cline (uvx)

Add to your .mcp.json or MCP config:

{
  "mcpServers": {
    "semantic-mcp": {
      "command": "uvx",
      "args": ["semantic-mcp", "serve", "--transport", "stdio"],
      "env": {
        "DISCOVERY_URL": "https://your-discovery-service",
        "DISCOVERY_API_KEY": "your-api-key"
      }
    }
  }
}

Claude Desktop (Docker)

{
  "mcpServers": {
    "semantic-mcp": {
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "DISCOVERY_URL", "-e", "DISCOVERY_API_KEY",
        "--add-host=host.docker.internal:host-gateway",
        "milkymap/semantic-mcp:0.2", "serve", "--transport", "stdio"
      ],
      "env": {
        "DISCOVERY_URL": "http://host.docker.internal:8000",
        "DISCOVERY_API_KEY": "your-key"
      }
    }
  }
}

Remote HTTP Server

Start the server:

semantic-mcp serve --transport streamable-http --host 0.0.0.0 --port 8001

Client configuration:

{
  "mcpServers": {
    "semantic-mcp": {
      "url": "http://your-server:8001/mcp"
    }
  }
}

Available Operations

semantic-mcp exposes a single semantic_router tool with these operations:

Discovery (lightweight)

Operation

Description

search_tools

Search for tools using natural language

search_servers

Search for servers using natural language

list_servers

List all registered servers

get_server_tools

List tools on a server

get_statistics

Get server/tool counts

Exploration (full details)

Operation

Description

get_server_info

Get detailed server information

get_tool_details

Get full tool schema and description

Lifecycle

Operation

Description

manage_server

Start or shutdown a server

list_running_servers

List currently running servers

Execution

Operation

Description

execute_tool

Execute a tool on a running server

poll_task_result

Check background task status

cancel_task

Cancel a running background task

list_tasks

List all background tasks

get_content

Retrieve offloaded content by reference ID

Workflow

1. DISCOVER    search_tools("your need")         → Find relevant tools
       ↓
2. EXPLORE     get_server_info(server)           → Check capabilities
               get_server_tools(server)          → List available tools
       ↓
3. UNDERSTAND  get_tool_details(server, tool)    → Get full schema (REQUIRED)
       ↓
4. START       manage_server(server, "start")    → Start the MCP server
       ↓
5. EXECUTE     execute_tool(server, tool, args)  → Run the tool
       ↓
6. CLEANUP     manage_server(server, "shutdown") → Stop when done (optional)

Important rules:

  • Always call get_tool_details before execute_tool to understand the schema

  • Always call manage_server(start) before executing tools

  • Use in_background=true for long-running operations, then poll_task_result

  • Large responses are automatically offloaded; use get_content(ref_id) to retrieve

Architecture

Component

Description

RuntimeEngine

Core runtime managing ZMQ communication and server lifecycle

DiscoveryClient

HTTP client for discovery service API

ContentManager

Large result offloading (text chunking, images)

BackgroundTasks

Priority queue for async tool execution

FastMCP

MCP server framework exposing tools to LLMs

Development

# Install with dev dependencies
uv sync --group dev

# Run tests
uv run pytest tests/ -v

License

MIT

A
license - permissive license
-
quality - not tested
D
maintenance

Maintenance

Maintainers
Response time
Release cycle
Releases (12mo)
Commit activity

Resources

Unclaimed servers have limited discoverability.

Looking for Admin?

If you are the server author, to access and configure the admin panel.

Latest Blog Posts

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