Tools registered with concrete `NewTool[In, Out]` types expose output schemas and

`structuredContent` only when the negotiated protocol is `2026-07-28` or newer.

Older or unknown protocols retain the original text responses without these

typed-output additions. Ordinary API and validation errors never expose the

SDK-generated zero-value structured output.

Handler-provided structured statuses are distinct from generated error output.

For example, `issue_write` can return `IsError: true` with

`status: "awaiting_user_submission"` while an MCP App form is pending. Modern

clients retain that explicit status and its reason; legacy clients retain the

stop message and error flag without structured content. This status does not

mean the issue was created or updated. The output schema includes a strict

status variant alongside the mutation's `id`/`url` variant. Multi-round-trip

`InputRequests` continue to pass through unchanged.