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MCP Lab

Getting Started

MCP Failure Lab requires Node.js 22.19.0 or newer and npm. The fastest path needs no clone or global install:

Terminal window
npx mcp-failure-lab demo

The demo runs a real deterministic 500ms delay through the built-in client, the SDK v2 in-process handler, the delay tool, and the assertion pipeline. Scenario execution targets MCP 2026-07-28.

Explore the CLI

Section titled “Explore the CLI”
Terminal window
npx mcp-failure-lab --help
npx mcp-failure-lab --version

Start the stdio server

Section titled “Start the stdio server”
Terminal window
npx mcp-failure-lab serve

The process waits silently for a client. Protocol messages use stdout, so operational diagnostics are written to stderr. Press Ctrl+C for graceful shutdown.

The stdio server supports MCP 2026-07-28 and retains 2025-11-25 compatibility.

Start the Streamable HTTP server

Section titled “Start the Streamable HTTP server”
Terminal window
npx mcp-failure-lab serve --transport http

The server listens at http://127.0.0.1:3000/mcp by default. Keep it bound to loopback unless a trusted reverse proxy provides authentication and TLS. See Streamable HTTP for configuration and Inspector setup.

Run an included scenario

Section titled “Run an included scenario”

From a repository checkout:

Terminal window
git clone https://github.com/anilloutombam/mcp-failure-lab.git
cd mcp-failure-lab
npm install
npm run dev -- run examples/scenarios/delay-success.json

Next: learn the scenario format or explore the fault tools.