This study evaluates the optimal monetary policy with an emphasis on the demand for money within the monetary rule in a small, open oil economy DSGE model, assuming heterogeneity among households and firms in their demand for money. Considering the heterogeneity of economic agents affects the transmission mechanisms of monetary policy due to differences in households' asset portfolios and firms' liquidity constraints, reducing the impact of monetary policy in the initial period of shock occurrence. Given heterogeneous economic agents, the framework of optimal monetary policy response to real and nominal shocks can be different. The least loss in implementing monetary policy in an oil shock condition occurs when the monetary base growth is chosen as the monetary policy tool and the demand for money growth is considered in the monetary rule. Meanwhile, the least loss in demand for money shock conditions is when the policy interest rate is selected as the monetary policy tool and the growth in demand for money is also considered in the monetary rule. the research results have two important policy recommendations. Firstly, the most important cause of demand for money instability, namely inflation expectations, must be managed. Secondly, financial markets should expand to provide greater access to financial resources for small and medium-sized enterprises.