LABSCO SUMMARY

Onchain investigation and Solidity work in the same session.

The reading half - traces, storage, decompiled bytecode - is where this earns its place: an unverified contract stops being opaque. The writing half is real too, and the project is blunt about the risk: give it a key with testnet funds only, because a model that hallucinates here spends money.

What it is

An MCP layer over the Foundry toolchain. It keeps a persistent Forge workspace at ~/.mcp-foundry-workspace, so Solidity files, scripts and installed dependencies survive between calls.

What you get

Start, stop and inspect a local Anvil instance, or point the same tools at any RPC endpoint
Read-only contract calls, transactions, receipts, raw storage slots and event logs
Replay a published transaction locally, and look up a function or event signature from the 4byte directory
Write Solidity into the workspace, install dependencies, and run a Forge script
Unit conversion between wei, gwei and hex, deployed-address computation, bytecode size and gas estimates
Heimdall analysis: disassemble bytecode, decode calldata without an ABI, decompile to Solidity, or draw a control flow graph

Requirements

Node.js v18+ and the Foundry toolchain (Forge, Cast, Anvil) installed. Heimdall-rs is needed only for the bytecode-analysis tools. Run it with npx @pranesh.asp/foundry-mcp-server. RPC_URL and PRIVATE_KEY are both optional environment variables - without a private key the server is read-only.

Setup effort

One command — npx @pranesh.asp/foundry-mcp-server

See installation options

USE CASES

01

Working out what an unverified contract does

Decompile the deployed bytecode to Solidity and an ABI, then disassemble the parts that still look wrong.

heimdall_decompileheimdall_disassembleheimdall_cfg

02

Explaining a transaction someone sent you

Pull the receipt, decode the calldata without needing an ABI, then replay the transaction locally to see the trace.

cast_receiptheimdall_decodecast_runheimdall_inspect

03

Trying a contract change against a local chain

Start Anvil, write the Solidity into the workspace, install what it imports, and run the Forge script against the local node.

anvil_startcreate_solidity_fileinstall_dependencyforge_script

04

Checking a deployment before you pay for it

Compute the address the contract would land on, estimate the gas, and check the bytecode size against the limit.

compute_addressestimate_gascontract_size

27 tools

Listed in project docs. Your client may show a different list.

anvil_start

anvil_stop

anvil_status

cast_call

cast_send

cast_balance

cast_receipt

cast_storage

cast_run

cast_logs

cast_sig

cast_4byte

cast_chain

forge_script

install_dependency

BEFORE YOU INSTALL

What to know first

Tools you get

27 tools named in the project's documentation. The five heimdall_ tools need heimdall-rs installed separately. cast_send, the only tool that writes to a chain, needs PRIVATE_KEY; without it the other twenty-six run read-only.

Requires

npx on PATH

INSTALLATION

Connect your client

Server setup

TERMINAL

npx @pranesh.asp/foundry-mcp-server

MCP Clients

Claude Code

CLAUDE CODE · TERMINAL

claude mcp add-json foundry-mcp-server '{"type":"stdio","command":"npx","args":["@pranesh.asp/foundry-mcp-server"],"env":{"RPC_URL":"","PRIVATE_KEY":""}}'

Cursor, Claude Desktop, Windsurf

JSON

{
  "mcpServers": {
    "foundry": {
      "command": "npx",
      "args": [
        "@pranesh.asp/foundry-mcp-server"
      ],
      "env": {
        "RPC_URL": "http://localhost:8545",
        "PRIVATE_KEY": "<YOUR_PRIVATE_KEY>"
      }
    }
  }
}

Claude Desktop — local build

CLAUDE DESKTOP — LOCAL BUILD · JSON

{
  "mcpServers": {
    "foundry": {
      "command": "node",
      "args": [
        "<YOUR_PATH_TO_FOUNDRY_MCP_SERVER>/dist/index.js"
      ],
      "env": {
        "PRIVATE_KEY": "0x1234"
      }
    }
  }
}

Foundry MCP Server