config

fastmcp.client.transports.config

Classes

MCPConfigTransport

Transport for connecting to one or more MCP servers defined in an MCPConfig.

This transport provides a unified interface to multiple MCP servers defined in an MCPConfig object or dictionary matching the MCPConfig schema. It supports two key scenarios:

1. If the MCPConfig contains exactly one server, it creates a direct transport to that server.
2. If the MCPConfig contains multiple servers, it creates a composite client by mounting all servers on a single FastMCP instance, with each server’s name, by default, used as its mounting prefix.

In the multiserver case, tools are accessible with the prefix pattern {server_name}_{tool_name} and resources with the pattern protocol://{server_name}/path/to/resource.

This is particularly useful for creating clients that need to interact with multiple specialized MCP servers through a single interface, simplifying client code.

Examples:

from fastmcp import Client

# Create a config with multiple servers
config = {
    "mcpServers": {
        "weather": {
            "url": "https://weather-api.example.com/mcp",
            "transport": "http"
        },
        "calendar": {
            "url": "https://calendar-api.example.com/mcp",
            "transport": "http"
        }
    }
}

# Create a client with the config
client = Client(config)

async with client:
    # Access tools with prefixes
    weather = await client.call_tool("weather_get_forecast", {"city": "London"})
    events = await client.call_tool("calendar_list_events", {"date": "2023-06-01"})

    # Access resources with prefixed URIs
    icons = await client.read_resource("weather://weather/icons/sunny")

Methods:

connect_session

connect_session(self, **session_kwargs: Unpack[SessionKwargs]) -> AsyncIterator[ClientSession]

close

close(self)