WEB3-329: chore: Add op-steel readme (#425)

crates/op-steel/README.md

@@ -0,0 +1,80 @@
+# OP-Steel
+
+A Rust library for integrating Optimism's Layer 2 blockchain with Steel, RISC Zero's production-ready smart contract execution prover.
+
+## Overview
+
+OP-Steel extends [Steel](https://github.com/risc0/risc0-ethereum/tree/main/crates/steel) to work with Optimism's Layer 2 blockchain and any OP Stack-compatible chains. Steel provides a generic tool to interact with EVM-compatible chains, enabling offchain execution of EVM apps while preserving onchain security through execution proofs.
+
+While you can use Steel directly to query and verify on the same chain (including OP chains), OP-Steel makes this process more convenient by including pre-configured OP network settings. The main advantage of OP-Steel, however, is its ability to perform **cross-chain queries** between Optimism and Ethereum, a feature not available in Steel alone.
+
+## Features
+
+- **Steel Integration**:
+  - Leverage Steel's execution proving system for Optimism L2 operations
+  - Generate verifiable proofs of correct smart contract execution
+  - Maintain onchain security while performing computation offchain
+- **Cross-Chain Queries**:
+  - Perform cross-chain queries between Optimism and Ethereum
+  - Seamlessly verify OP contract execution on Ethereum L1
+- **Dispute Game Integration**:
+  - Find and validate dispute games
+  - Support for latest, finalized, and specific game indices
+  - Automatic verification against the L1 `OptimismPortal` contract
+- **OP Stack Compatibility**:
+  - Use OP-Steel with OP-Mainnet and any OP Stack-compatible chains
+
+## Usage
+
+Usage of OP-Steel is very similar to Steel. See the [Steel README](https://github.com/risc0/risc0-ethereum/tree/main/crates/steel#readme) for more details.
+
+### Querying and Verifying on the Same Chain
+
+If you only need to query and verify on the same chain (e.g., OP-Mainnet), you can use Steel directly. However, OP-Steel simplifies this process by providing pre-configured OP network settings.
+
+```rust
+// Create an OP environment
+let env = OpEvmEnv::builder()
+    .rpc(Url::parse("https://optimism-rpc.publicnode.com")?)
+    .build()
+    .await?
+    // Apply chain configuration
+    .with_chain_spec(&OP_MAINNET_CHAIN_SPEC);
+
+// Implement steel functionality
+let contract = Contract::new(CONTRACT, &env);
+contract.call_builder(&CALL).from(CALLER).call();
+
+// Convert to input format for the guest
+let input = env.into_input().await?;
+```
+
+### Cross-Chain Queries (OP to Ethereum)
+
+OP-Steel enables cross-chain queries, such as verifying OP contract execution on Ethereum L1. This is a key feature that Steel alone does not provide.
+
+```rust
+// Create an OP environment referencing a dispute game
+let env = OpEvmEnv::builder()
+    .dispute_game_from_rpc(
+        portal_address,
+        "https://ethereum-rpc.publicnode.com".parse()?
+    )
+    .rpc("https://optimism-rpc.publicnode.com".parse()?)
+    .game_index(DisputeGameIndex::Latest)
+    .build()
+    .await?;
+
+// Implement steel functionality
+let contract = Contract::new(CONTRACT, &env);
+contract.call_builder(&CALL).from(CALLER).call();
+
+// Convert to input format for the guest
+let input = env.into_input().await?;
+```
+
+## Learn More
+
+- [Steel Documentation](https://github.com/risc0/risc0-ethereum/tree/main/crates/steel#readme) - Learn about the core Steel system
+- [RISC Zero Developer Docs](https://dev.risczero.com/api/) - Detailed documentation about the underlying zkVM
+- [Optimism Documentation](https://community.optimism.io/) - Learn about Optimism's L2 system

examples/README.md

@@ -1,22 +1,45 @@
 # Examples
-This directory includes three example uses of Steel. Each example demonstrates a different concept of Steel. 
 
-## [ERC20 Balance Query](./erc20/README.md)
+This directory includes three example uses of Steel. Each example demonstrates a different concept of Steel.
 
-This introductory example illustrates how to use [Steel] to directly query the `balanceOf` function of any ERC20 token contract, providing a verifiable proof of a user's token balance.
+### [ERC20 Balance Query](./erc20/README.md)
 
-## [ERC20 Counter with Off-Chain Proofs](./erc20-counter/README.md)
+This introductory example illustrates how to use [Steel] to directly query the `balanceOf` function of any ERC20 token
+contract, providing a verifiable proof of a user's token balance.
+
+### [ERC20 Counter with Off-Chain Proofs](./erc20-counter/README.md)
+
+Explore a more advanced interaction between [Steel] and a custom Ethereum smart contract. This counter contract utilizes
+off-chain [Steel] proofs to:
 
-Explore a more advanced interaction between [Steel] and a custom Ethereum smart contract. This counter contract utilizes off-chain [Steel] proofs to:
 - Increment a counter based on user-submitted proofs.
 - Verify ERC20 token ownership (minimum 1 token required) before incrementing.
 - Leverage RISC Zero as a [coprocessor] for efficient proof generation and verification.
 
-## [Compound Token Stats (APR Proof)](./token-stats/README.md)
+### [Compound Token Stats (APR Proof)](./token-stats/README.md)
 
 This example shows how the [Steel] library can be used to call multiple view functions of a contract.
-This example generates a proof of a [Compound] cToken's APR (Annual Percentage Rate), showcasing the potential for on-chain verification of complex financial metrics.
+This example generates a proof of a [Compound] cToken's APR (Annual Percentage Rate), showcasing the potential for
+on-chain verification of complex financial metrics.
+
+## ERC20 Balance Query using [op-steel]
+
+### [L2 Execution - L2 Verification](./op/l2)
+
+This example shows how to use [op-steel] to query the `balanceOf` function of an ERC20 token on OP, providing a proof
+that can be verified on OP.
+
+### [L1 Execution - L2 Verification](./op/l1-to-l2)
+
+This example shows how to use [op-steel] to query the `balanceOf` function of an ERC20 token on Ethereum and how the
+generated proof can be verified on OP.
+
+### [L2 Execution - L1 Verification](./op/l2-to-l1)
+
+This example shows how to use [op-steel] to query the `balanceOf` function of an ERC20 token on OP and how the generated
+proof can be verified on Ethereum.
 
 [coprocessor]: https://risczero.com/blog/a-guide-to-zk-coprocessors-for-scalability
 [Steel]: ../crates/steel
 [Compound]: https://compound.finance/
+[op-steel]: ../crates/op-steel