Registering Your Contract’s Method Names
MetaMask uses the parity on-chain registry of function signatures to display method names on the confirm screen. For many common method names, like token methods, this allows MetaMask to successfully look up the method names by their method signature. However, sometimes you’re using a method that is not in that on-chain registry, and MetaMask will simply display
Unknown Function to the user.
To add your contract’s function names to this registry so it shows in the MetaMask interface, follow the below steps.
Use etherscan’s write contract feature to input the string value (without quotes or spaces) to the register function
Approve the transaction through MetaMask (you only pay gas)
web3.sha3('getOwners()') => 0xa0e67e2bdc0a6d8a09ccd6c353c9df590807ad66ff5e6630c4f31a86dfa84821
take the first 10 characters
and input into this demo app that checks the on-chain registry (mainnet or rinkeby)
Alternate steps using remix.ethereum.org:
Set the correct compiler version based on the contract.
Use remix’s write functionality to add to the registry.
You can look at the FUNCTIONHASHES section on remix.ethereum.org by loading the signature registry contract, press the Details button on the compile tab.
You can also use the signature registry deployed on rinkeby but should note that MetaMask reads from the mainnet eth-method-registry endpoint, regardless of user’s network
eth-method-registry is used to lookup methods in MetaMask.
This stack exchange answer is a good tldr.