Function validate_output 

pub fn validate_output(
    api_version: &str,
    operation_id: &str,
    data: &Value,
) -> Result<(), McpifyError>

Returns Err if data doesn’t satisfy operation_id’s output schema — surfaces upstream API drift as a structured error rather than silently returning a mismatched response (architecture.md’s call pipeline). Validates against the given api_version’s schema.