Optional result-level _meta object. Reserved by MCP on every Result
(the base interface all paginated list results extend), so it round-trips
on every protocol version: toJson emits it only when set and fromJson
parses it. Unset by default, so pre-existing wire output is unchanged.
Optional result-level _meta object. Reserved by MCP on every Result (the base interface all paginated list results extend), so it round-trips on every protocol version: toJson emits it only when set and fromJson parses it. Unset by default, so pre-existing wire output is unchanged.