Update documentation on COAs (#740)

docs/evm/build/accounts.md

@@ -16,17 +16,40 @@ There are three types of accounts used for EVM on Flow.
 
 1. **Externally Owned Accounts (EOA)**: EOAs are controlled by private individuals using cryptographic keys and can initiate transactions directly. They are the primary account type for users to interact with the blockchain, holding and sending cryptocurrency or calling smart contract functions.
 2. **Contract Accounts**: These accounts hold smart contract code and are governed by this code's logic. Unlike EOAs, Contract Accounts do not initiate transactions on their own but can execute transactions in response to calls they receive from EOAs or other contracts.
-3. **Cadence Owned Accounts (COA)**
+3. **Cadence Owned Accounts (COA)**: This is an account type unique to Flow EVM. These accounts are managed by [Cadence resources](https://cadence-lang.org/docs/1.0/language/resources) and can be used to interact with the Flow EVM from within the Cadence environment.
 
-EOAs and Contract accounts function the same as on other EVM networks.  Read more about EOAs and Contract accounts on the [Ethereum docs](https://ethereum.org/developers/docs/accounts). EVM developers can use EVM on Flow without having to use COAs. However, in order to leverage all the features of Cadence, developers will need to utilize Cadence Owned Accounts.
+EOAs and Contract accounts function the same as on other EVM networks. Users may interact with these accounts using the standard EVM JSON-RPC API ([see endpoints here](../using.mdx)). You can read more about EOAs and Contract accounts on the [Ethereum docs](https://ethereum.org/developers/docs/accounts).
+
+However, in order to leverage all the features of Cadence, developers will need to utilize Cadence Owned Accounts.
 
 ## Cadence Owned Accounts
 
-Cadence Owned Accounts (COAs) are a new account type on Flow which mediates interactions between EVM and Cadence  environments. COAs are intended for use by end-users, the same as EOAs. However, COAs execute EVM transactions as directed from Cadence whereas EOAs run EVM transactions identically to other EVMs via the JSON-RPC endpoint.
-Unlike EOAs, COAs do not have a key but are assigned a 20-byte EVM address upon creation from Cadence.
+A Cadence Owned Account (COA) is a natively supported EVM smart contract wallet type that allows a Cadence resource to own and control an EVM address. This native wallet type provides the primitives needed to bridge or control assets across Flow EVM and Cadence facilitating composability between environments.
 
-COAs exist in Cadence as a Resource type which is in turn owned by a Flow account on the Cadence VM. COAs facilitate the execution of EVM transactions using its `run` method. They also enable the deployment of Solidity contracts from Cadence, as well as other utility functions to interact with EVM.
+![Account-Model](flow-evm-account-model.png)
 
-For more information on Cadence Owned Accounts, see the [Flow EVM Support FLIP](https://github.com/onflow/flips/pull/225/files)
+### Why use COAs?
 
-![Account-Model](flow-evm-account-model.png)
+COAs create powerful new opportunities to improve the UX, functionality and utility of EVM applications by taking advantage of Cadence. Key benefits include:
+
+- **Enhanced Composability**: Applications written in Solidity can be extended and composed upon within Cadence. This allows developers to build upon existing EVM applications and deliver a more feature-rich user experience.
+
+- **Atomic Interactions**: Developers are able to execute multiple EVM transactions atomically from a COA, which is not possible using traditional EVM accounts. This is particularly useful for applications that require multiple transactions to be executed within a single block, or require that prior transactions' state changes revert if a subsequent transaction fails.
+
+- **Native Account Abstraction**: COAs are controlled by Cadence resources, which are in turn owned by Flow accounts. [Flow accounts](../build/accounts.md) have built-in support for multi-signature authentication, key rotation, and account recovery. As a Cadence resource, COAs naturally inherit [these features](https://developers.flow.com/build/differences-vs-evm/account-abstraction).
+
+- **Fine-Grained Access Control**: As Cadence resources, access to a COA can be governed by more sophisticated policies than those available with basic EVM accounts. By utilizing powerful Cadence access control primitives such as [capabilities and entitlements](https://cadence-lang.org/docs/1.0/language/access-control), developers can restrict who is able to interact with a COA and what actions they are permitted to perform.
+
+### Differences from Traditional EVM Accounts
+
+COAs are smart contracts that are deployed to, and are fully accessible within, Flow EVM. However, unlike traditional EVM accounts (e.g. EOAs or smart contract accounts), COAs are owned by a Cadence resource. This means that COAs can be created and controlled natively within the Cadence execution enviornment.
+
+Unlike EOAs, COAs do not have an associated key, but are assigned a 20-byte EVM address upon creation from Cadence. This address is based on the UUID of the Cadence resource and is prefixed with `0x000000000000000000000002`. This address determines the location of the COA smart contract deployment and is the EVM address that is used to interact with the COA.
+
+A COA may instantiate transactions itself (where the COA's EVM address acts as `tx.origin`). This behaviour differs from other EVM environments, where only externally owned accounts (EOAs) may instantiate transactions. A new EVM transaction type (`TxType=0xff`) is used to differentiate COA transactions from other types of EVM transactions (e.g. DynamicFeeType where `TxType=0x02`).
+
+Because COAs are owned by Cadence resources, an EVM transaction is not required to trigger a transaction from a COA (e.g. a transaction to make a call to `execute` or EIP-4337's `validateUserOpMethod`). Instead, call transactions may be triggered directly from the Cadence resource that owns the COA. By invoking the `call` method on this resource, a transaction event will be emitted within the EVM environment.
+
+### More Information
+
+For more information on Cadence Owned Accounts, see the [Flow EVM Support FLIP](https://github.com/onflow/flips/pull/225/files)