Macro rpc_invalid_params 

macro_rules! rpc_invalid_params {
    ($message:expr, $id:expr) => { ... };
    ($message:expr) => { ... };
}

Common error response shortcuts using predefined error codes

Usage:

rpc_invalid_params!("Expected array of two numbers", id)
rpc_method_not_found!(id)
rpc_parse_error!("Invalid JSON", id)
rpc_internal_error!("Database connection failed", id)