Foundry is a command-line toolkit for Ethereum smart-contract development: forge compiles, tests, fuzzes and deploys Solidity contracts, cast calls contracts and sends transactions, anvil runs a local node, and chisel is a Solidity REPL. Use when a user asks to set up a Foundry project, write Solidity unit or fuzz tests, fork mainnet in a test, deploy with forge script, verify a contract on Etherscan, track gas with forge snapshot, or read and write chain state with cast.
