# Contracts should inherit their interfaces Low/Info · Three Sigma · NFT perpetuals · 2nd January, 2024 Finding 3S-NFTPerp-N05 of the Nftperp Exchange security review. - Report: /reports/nftperp-i - Source: https://cdn.sanity.io/files/qoqld077/production/c19530de75e234ad15694b4563edb1fc9d2a3fd8.pdf --- ### Description To avoid differences between the function declarations in the contracts and their interfaces, it is a good practice for contracts to inherit their interfaces. At the moment the [AMM](https://github.com/nftperp/NFTPerp-V2-Contracts/blob/1c16f2010a851ac23aec73822d55388901bbe5e7/src/AMM.sol) contract doesn't inherit the [IAMM](https://github.com/nftperp/NFTPerp-V2-Contracts/blob/1c16f2010a851ac23aec73822d55388901bbe5e7/src/interfaces/IAMM.sol) interface and this leads to problems of functions existing in the interface but not the contract. For instance, functions getInitializationPrice(), getLiquidationParams() and getReservesAndTotalLiquidity(). In the future a user might try to interact with the protocol using the interface, but the call would certainly revert due to this issue. ### Status Acknowledged --- Related findings: - [Some contracts don't implement their entire interface](https://0xsimao.com/findings/m-0-don-implement-entire-interface): M^0 Minter Gateway