Add NatSpec documentation to StdChains methods

src/StdChains.sol

@@ -65,7 +65,13 @@ abstract contract StdChains {
 
     bool private fallbackToDefaultRpcUrls = true;
 
-    // The RPC URL will be fetched from config or defaultRpcUrls if possible.
+    /// @dev Retrieves chain configuration by alias. RPC URL is resolved using the prioritization
+    ///      hierarchy: setChain > foundry.toml > environment variable > defaults.
+    ///      Triggers lazy initialization of default chains on first call.
+    /// @param chainAlias The chain alias (e.g., "mainnet", "sepolia"). Must match the alias in
+    ///                   foundry.toml [rpc_endpoints] section for config-based resolution.
+    /// @return chain The chain configuration with resolved RPC URL.
+    /// @custom:reverts If chainAlias is empty or chain not found in the registry.
     function getChain(string memory chainAlias) internal virtual returns (Chain memory chain) {
         require(bytes(chainAlias).length != 0, "StdChains getChain(string): Chain alias cannot be the empty string.");
 
@@ -79,6 +85,12 @@ abstract contract StdChains {
         chain = getChainWithUpdatedRpcUrl(chainAlias, chain);
     }
 
+    /// @dev Retrieves chain configuration by chain ID. First resolves chainId to its alias via
+    ///      the internal mapping, then delegates to getChain(string). RPC URL resolution follows
+    ///      the same prioritization hierarchy: setChain > foundry.toml > env var > defaults.
+    /// @param chainId The chain ID (e.g., 1 for mainnet, 11155111 for sepolia).
+    /// @return chain The chain configuration with resolved RPC URL.
+    /// @custom:reverts If chainId is 0 or chain not found in the registry.
     function getChain(uint256 chainId) internal virtual returns (Chain memory chain) {
         require(chainId != 0, "StdChains getChain(uint256): Chain ID cannot be 0.");
         initializeStdChains();
@@ -94,7 +106,13 @@ abstract contract StdChains {
         chain = getChainWithUpdatedRpcUrl(chainAlias, chain);
     }
 
-    // set chain info, with priority to argument's rpcUrl field.
+    /// @dev Sets custom chain configuration for the given alias. If chain.rpcUrl is provided, it takes
+    ///      priority in subsequent getChain calls. Creates bidirectional mappings (alias <-> chainId).
+    ///      Overwrites existing configuration if the alias already exists.
+    /// @param chainAlias The chain alias to register (must be non-empty).
+    /// @param chain The chain data including name, chainId, and optional rpcUrl.
+    /// @custom:reverts If chainAlias is empty, chainId is 0, or chainId is already mapped to a different alias.
+    /// @custom:sideeffects Updates chains[chainAlias] and idToAlias[chainId] mappings. Removes old chainId mapping if alias is being updated.
     function setChain(string memory chainAlias, ChainData memory chain) internal virtual {
         require(
             bytes(chainAlias).length != 0,
@@ -127,7 +145,12 @@ abstract contract StdChains {
         idToAlias[chain.chainId] = chainAlias;
     }
 
-    // set chain info, with priority to argument's rpcUrl field.
+    /// @dev Convenience overload that accepts a Chain struct instead of ChainData. Extracts the
+    ///      relevant fields and delegates to setChain(string, ChainData). Behavior is identical
+    ///      regarding RPC URL priority and mapping updates.
+    /// @param chainAlias The chain alias to register (must be non-empty).
+    /// @param chain The Chain struct including name, chainId, chainAlias, and optional rpcUrl.
+    /// @custom:reverts Same conditions as setChain(string, ChainData).
     function setChain(string memory chainAlias, Chain memory chain) internal virtual {
         setChain(chainAlias, ChainData({name: chain.name, chainId: chain.chainId, rpcUrl: chain.rpcUrl}));
     }
@@ -146,8 +169,12 @@ abstract contract StdChains {
         return string(copy);
     }
 
-    // lookup rpcUrl, in descending order of priority:
-    // current -> config (foundry.toml) -> environment variable -> default
+    /// @dev Internal helper that resolves the RPC URL for a chain using the prioritization hierarchy.
+    ///      Priority order: current chain.rpcUrl > foundry.toml config > environment variable > default.
+    ///      Environment variable format: {UPPERCASE_ALIAS}_RPC_URL (e.g., MAINNET_RPC_URL).
+    /// @param chainAlias The chain alias used for config and env var lookups.
+    /// @param chain The chain struct, potentially with an empty rpcUrl to be resolved.
+    /// @return The chain struct with rpcUrl populated from the highest priority available source.
     function getChainWithUpdatedRpcUrl(string memory chainAlias, Chain memory chain)
         private
         view
@@ -184,10 +211,18 @@ abstract contract StdChains {
         return chain;
     }
 
+    /// @dev Configures whether to fall back to default RPC URLs when foundry.toml config is unavailable.
+    ///      When set to false, getChain will revert if the environment variable is not set and no
+    ///      config exists. Default value is true.
+    /// @param useDefault If true, falls back to default RPC URLs; if false, requires explicit config or env var.
     function setFallbackToDefaultRpcUrls(bool useDefault) internal {
         fallbackToDefaultRpcUrls = useDefault;
     }
 
+    /// @dev Lazy initialization function that populates the default chain registry on first use.
+    ///      Called automatically by getChain and setChain. Uses a guard flag to ensure initialization
+    ///      happens exactly once per contract instance.
+    /// @custom:chains Initializes 50+ chains including mainnet, testnets, and L2s with default RPC URLs.
     function initializeStdChains() private {
         if (stdChainsInitialized) return;
 
@@ -292,7 +327,11 @@ abstract contract StdChains {
         );
     }
 
-    // set chain info, with priority to chainAlias' rpc url in foundry.toml
+    /// @dev Internal helper used during initialization to register chains with default RPC URLs.
+    ///      Stores the default URL separately and clears chain.rpcUrl to enable config-based resolution.
+    ///      This ensures foundry.toml and env vars take priority over defaults.
+    /// @param chainAlias The chain alias to register.
+    /// @param chain The chain data with a default RPC URL.
     function setChainWithDefaultRpcUrl(string memory chainAlias, ChainData memory chain) private {
         string memory rpcUrl = chain.rpcUrl;
         defaultRpcUrls[chainAlias] = rpcUrl;