Foundry MCP Server

What is Foundry MCP Server?

Foundry MCP Server is a lightweight MCP server that connects LLM assistants to the Foundry toolchain (Forge, Cast, Anvil), enabling Solidity development and onchain operations. It is designed for developers who want to interact with Ethereum nodes, analyze smart contracts, and manage Solidity code through natural language interfaces.

How to use Foundry MCP Server?

Install globally via npm install -g @pranesh.asp/foundry-mcp-server or run directly with npx @pranesh.asp/foundry-mcp-server. Configure your MCP client (e.g., Claude Desktop, Cursor) by adding a "foundry" entry under mcpServers in your client’s configuration file, providing the command npx with arguments and optional environment variables RPC_URL and PRIVATE_KEY. The server uses STDIO transport and requires Node.js v18+, the Foundry toolchain, and optional Heimdall-rs for advanced analysis.

Key features of Foundry MCP Server

• Start and manage local Anvil instances
• Connect to remote RPC endpoints and query chain info
• Call contract functions (read-only) and send transactions
• Maintain a persistent Forge workspace at ~/.mcp-foundry-workspace
• Create, edit, and deploy Solidity files and scripts
• Disassemble, decode, and decompile EVM bytecode via Heimdall

Use cases of Foundry MCP Server

• Analyze on-chain transactions and explain their behavior
• Query token balances (e.g., ETH and USDT) for any wallet
• Deploy mock ERC20 contracts to a local Anvil instance
• Run Forge scripts and manage Solidity dependencies

FAQ from Foundry MCP Server

What runtime and tools does Foundry MCP Server require?

Node.js v18+, the Foundry toolchain (Forge, Cast, Anvil), and optionally Heimdall-rs for contract analysis.

Is a private key required to use the server?

No, the PRIVATE_KEY environment variable is optional. If set, it enables sending transactions. The README strongly advises against using keys with mainnet funds due to LLM hallucination risks.

Where does the server store Solidity files and projects?

It maintains a persistent Forge workspace at ~/.mcp-foundry-workspace for all Solidity files, scripts, and dependencies.

How do I configure a client like Claude Desktop?

Add a JSON entry under mcpServers with command npx, arguments ["@pranesh.asp/foundry-mcp-server"], and optional environment variables for RPC_URL and PRIVATE_KEY. Ensure valid JSON syntax.

What transport protocol does Foundry MCP Server use?

It uses STDIO transport, as shown in the MCP client configuration examples.