Function call_worker 

pub async fn call_worker(
    state: &Arc<ServerState>,
    tool: &str,
    selector: &str,
    method: &str,
    params: Value,
) -> Result<(Value, AddressCanonicalizer), ErrorEnvelope>

Run one tool call. selector is the poison/short-circuit key component (e.g. the function arg, or the program_path); pass "" for selector-less calls. Returns (result_value, canon_snapshot).