Validate a CallToolResult's structuredContent against tool's
outputSchema, independent of the opt-in flag. Returns an empty string
when it conforms (including when the tool has no output schema or the
result has no structured content), otherwise a description of the first
violation. Exposed so callers can validate explicitly without enabling
automatic validation.
Validate a CallToolResult's structuredContent against tool's outputSchema, independent of the opt-in flag. Returns an empty string when it conforms (including when the tool has no output schema or the result has no structured content), otherwise a description of the first violation. Exposed so callers can validate explicitly without enabling automatic validation.