update docs

README.md

@@ -21,6 +21,22 @@ Smart account with programmable ownership
 - [ZodiacMech.sol](contracts/ZodiacMech.sol): allow enabled [zodiac](https://github.com/gnosis/zodiac) modules to sign transactions on behalf of the Mech
 - [Mech.sol](contracts/base/Mech.sol): implement custom ownership terms by extending this abstract contract
 
+## Mech interface
+
+Mech implements the [EIP-4337](https://eips.ethereum.org/EIPS/eip-4337) account interface, [EIP-1271](https://eips.ethereum.org/EIPS/eip-1271), and the following functions:
+
+### `isOperator(address signer)`
+
+Returns true if `signer` is allowed to operate the Mech.
+Sub classes implement this function for defining the specific operator criteria.
+
+### `exec(address to, uint256 value, bytes data, Enum.Operation operation, uint256 txGas)`
+
+Allows the operator to make the Mech execute a transaction.
+
+- `operation: 0` for a regular call
+- `operation: 1` for a delegate call
+
 ## Contribute
 
 The repo is structured as a monorepo with `mech-contracts` as the container package exporting the contract sources and artifacts.
@@ -75,8 +91,6 @@ Mech implements the EIP-4337 [Account](contracts/base/Account.sol) interface mea
 For this purpose the EIP-4337 entry point contract first calls the Mech's `validateUserOp()` function for checking if a user operation has a valid signature by the mech operator.
 The entry point then calls the `exec` function, or any other function using the `onlyOperator` modifier, to trigger execution.
 
-### EIP-6551 token-bound account
-
 ### EIP-1271 signatures
 
 [Mech](contracts/base/Mech.sol) implements the EIP-1271 interface.
@@ -104,13 +118,19 @@ This enables counterfactually funding the mech account (own token to unlock trea
 
 The deterministic deployment is implemented via Zodiac's [ModuleProxyFactory](https://github.com/gnosis/zodiac/blob/master/contracts/factory/ModuleProxyFactory.sol), through which each mech instance is deployed as an ERC-1167 minimal proxy.
 
+### EIP-6551 token-bound account
+
+The token-bound versions of Mech adopts the [EIP-6551](https://eips.ethereum.org/EIPS/eip-6551) standard.
+This means that these kinds of mechs are deployed through the official 6551 account registry, so they are deployed to the canonical address and detected by compatible tools.
+
 ### EIP-1167 minimal proxies with context
 
 The holder of the token gains full control over the mech account and can write to its storage without any restrictions via delegate calls.
 Since tokens are transferrable this is problematic, as a past owner could mess with storage to change the mech's behavior in ways that future owners wouldn't expect.
 That's why the ERC721 and ERC1155 versions of mech avoid using storage but instead solely rely on the immutable data in their own bytecode.
 
 To achieve this, mechs are deployed through a version of a EIP-1167 proxy factory that allows appending arbitrary bytes to the minimal proxy bytecode.
+The same mechanism is implemented by the 6551 account registry.
 
 ### Migrate a Safe to a ZodiacMech
 

contracts/interfaces/IMech.sol

@@ -6,6 +6,12 @@ import "@gnosis.pm/safe-contracts/contracts/common/Enum.sol";
 import "@account-abstraction/contracts/interfaces/IAccount.sol";
 
 interface IMech is IAccount, IERC1271 {
+    /**
+     * @dev Return if the passed address is authorized to sign on behalf of the mech, must be implemented by the child contract
+     * @param signer The address to check
+     */
+    function isOperator(address signer) external view returns (bool);
+
     /// @dev Executes either a delegatecall or a call with provided parameters
     /// @param to Destination address.
     /// @param value Ether value.