Connecting to MCP Servers - ModRouter

Overview

ModRouter can connect to MCP-compatible servers and make their tools available to AI requests. A connected MCP server can be local, remote, or streaming.

Type	Description	Best for
`stdio`	Starts a local process and talks over stdin/stdout	Local tools, scripts, filesystem MCP servers
`http`	Connects to an HTTP MCP endpoint	Remote APIs and hosted MCP servers
`sse`	Connects to an SSE MCP endpoint	Servers that keep a streaming connection open

STDIO Server

{
  "mcp": {
    "client_configs": [
      {
        "name": "filesystem",
        "connection_type": "stdio",
        "stdio_config": {
          "command": "npx",
          "args": ["-y", "@anthropic/mcp-filesystem"],
          "envs": ["HOME", "PATH"]
        },
        "auth_type": "none",
        "tools_to_execute": ["*"]
      }
    ]
  }
}

When ModRouter runs in Docker, STDIO tools must be installed inside the container. If the command is not available in the container, use an HTTP or SSE MCP server instead.

HTTP Server

{
  "mcp": {
    "client_configs": [
      {
        "name": "web_search",
        "connection_type": "http",
        "connection_string": "https://mcp.example.com/mcp",
        "auth_type": "none",
        "tools_to_execute": ["search", "fetch_url"]
      }
    ]
  }
}

SSE Server

{
  "mcp": {
    "client_configs": [
      {
        "name": "live_data",
        "connection_type": "sse",
        "connection_string": "https://mcp.example.com/sse",
        "auth_type": "none",
        "tools_to_execute": ["*"]
      }
    ]
  }
}

Authentication

For HTTP and SSE servers, choose the authentication mode that matches the upstream MCP server:

Use Tools in Inference Requests

Once an MCP server is connected, ModRouter can make its tools available to chat and responses requests.

export MODROUTER_BASE_URL="https://api.modrouter.online"
export MODROUTER_API_KEY="<your-modrouter-virtual-key>"

curl --location "https://api.modrouter.online/v1/chat/completions" \
  --header "Authorization: Bearer ${MODROUTER_API_KEY}" \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "openai/gpt-4o-mini",
    "messages": [
      { "role": "user", "content": "Use the available tools to answer this question." }
    ],
    "tool_choice": "auto"
  }'

Use Tool Filtering to choose which connected tools are available for a request.