See the Build an MCP client tutorial for more information.

call_tool validates every result against the tool's declared output schema, so the spec's client-side SHOULD needs no code here.

The two channels go to different readers: content is forwarded to the model, while structured_content is used as data — when a tool returns an array, the client counts its items rather than re-reading the prose. See Structured Content.

Client(transport, mode="auto") probes server/discover and falls back to the 2025-11-25 handshake; client.protocol_version reports which era you got. See Protocol versions.