Pact MCP Server

pact-mcp — MCP servers for Pact & Chainweb

Model Context Protocol servers that give your AI agent safe, auditable access to the Pact 5 development loop on Kadena Chainweb.

Run REPL tests, scan modules for critical language traps, estimate gas, and query or submit to Chainweb nodes — from Claude, Cursor, VS Code, or any MCP-compatible client. Every tool runs behind a strict, tested security baseline, and no tool ever touches a private key.

{
  "mcpServers": {
    "pact": {
      "command": "npx",
      "args": ["-y", "@pact-community/mcp-pact"],
      "env": { "PACT_COMMUNITY_WORKSPACE_ROOT": "/path/to/your/project" }
    }
  }
}

Servers

Both are listed in the official MCP registry as io.github.Pact-Community-Organization/pact and io.github.Pact-Community-Organization/chainweb.

Install

VS Code (one click)

Using VS Code with GitHub Copilot? Install with a single click:

The button opens VS Code and pre-fills the configuration. You can also search the MCP Servers view, or add from the command line:

code --add-mcp '{"name":"pact","command":"npx","args":["-y","@pact-community/mcp-pact"],"env":{"PACT_COMMUNITY_WORKSPACE_ROOT":"${workspaceFolder}","PACT_COMMUNITY_PACT_BIN":"pact"}}'

On VS Code Insiders, use vscode-insiders: in the links or code-insiders on the command line.

Claude Code

claude mcp add pact -e PACT_COMMUNITY_WORKSPACE_ROOT=/path/to/your/project \
  -- npx -y @pact-community/mcp-pact

Any MCP client

Add both servers to your client configuration:

{
  "mcpServers": {
    "pact": {
      "command": "npx",
      "args": ["-y", "@pact-community/mcp-pact"],
      "env": {
        "PACT_COMMUNITY_WORKSPACE_ROOT": "/path/to/your/project",
        "PACT_COMMUNITY_PACT_BIN": "pact"
      }
    },
    "chainweb": {
      "command": "npx",
      "args": ["-y", "@pact-community/mcp-chainweb"],
      "env": {
        "PACT_COMMUNITY_WORKSPACE_ROOT": "/path/to/your/project",
        "PACT_COMMUNITY_CHAINWEB_MODE": "devnet",
        "PACT_COMMUNITY_CHAINWEB_PROFILE": "devnet",
        "PACT_COMMUNITY_CHAINWEB_BASE_URL": "http://localhost:8081",
        "PACT_COMMUNITY_CHAINWEB_NETWORK_ID": "development"
      }
    }
  }
}

Each server's README documents its full tool list and environment variables: Pact Tooling · Chainweb API.

Your first 10 minutes

1. Install the Pact CLI — Pact Tooling uses it for REPL runs and gas estimation. Download a release from kadena-io/pact-5, put pact on your PATH, and verify with pact --version.
2. Add the servers to your client with the config above, pointing PACT_COMMUNITY_WORKSPACE_ROOT at your contract project.
3. Ask your agent:
   • "Scan contracts/token.pact for critical Pact 5 traps" — flags non-binary +, DB reads inside enforce, built-in shadowing, and more.
   • "Run tests/token.repl and summarize the failures" — executes the file with the real Pact interpreter and parses the results.
   • "Diff the public interface of token.pact against token-v2.pact" — reports added/removed/changed functions and whether the change is breaking.
   • "What's the current block height on chain 0?" — queries a Chainweb node.

Everything in Pact Tooling works with just the CLI — no node required. Chainweb API works against any Chainweb-compatible node: point PACT_COMMUNITY_CHAINWEB_BASE_URL at your devnet, or use the read-only testnet06 / mainnet profiles to query public networks.

Security

Both servers enforce the same tested baseline (details in SECURITY.md):

• No private keys, ever. chainweb_send, chainweb_deploy_module, and chainweb_continue_pact require transactions to be signed externally (Ledger, @kadena/client, …) and passed in pre-signed.
• Read-only public networks. The testnet06 and mainnet profiles block every write tool with PROFILE_WRITE_BLOCKED.
• Audit logging of every tool call with SHA-256 input hashes (never raw inputs).
• Prompt-injection stripping on all tool output before it reaches the model.
• Tool-schema locking — a server refuses to start if its tool schemas drift.
• Network and filesystem allowlists, no shell execution, and refusal to run as root.

Compatibility

Contributing

git clone https://github.com/Pact-Community-Organization/pact-mcp.git
cd pact-mcp
pnpm install
pnpm build
pnpm test

Requires Node.js >= 20.11 and pnpm >= 9. See CONTRIBUTING.md for workflow, coding standards, and how to add or change a tool.

License

Apache-2.0