ClientGroup coordinates several independent FastMCP clients without combining them behind a proxy server. Each client keeps its own connection, negotiated protocol version, capabilities, and handlers. The group adds namespaced tool discovery and routes each call back to the client that advertised the tool.
This differs from passing a multi-server configuration directly to Client. Client(config) presents one aggregate MCP endpoint and therefore selects one protocol era shared by its proxy chain. A ClientGroup retains one MCP connection per configured server, so legacy and modern servers can operate in their native eras at the same time.