devenv-doctor-mcp

An MCP server that gives an LLM client (Claude, or any MCP-compatible host) the ability to actually inspect your local dev environment — Docker container health, pnpm workspace integrity, and stuck/hung processes — instead of you copy-pasting terminal output back and forth.

Built for the MCP to the Moon hackathon.

Why this exists

While building this, I hit a real pnpm bug: pnpm self-update corrupted my global environment lockfile, and every single pnpm invocation started crashing with Cannot use 'in' operator to search for 'integrity' in undefined. Diagnosing it meant manually hunting through ~/.local/share/pnpm, checking process states, and re-running commands with debug flags — exactly the kind of repetitive, mechanical diagnosis an LLM with the right tools could do directly. This project is that toolset.

Related MCP server: Rebrain MCP Server

What it does

Four tools, exposed over MCP:

ping

Sanity check — confirms the server is alive and the connection works.

check_docker_status

Given a container name (and optionally an expected host port), reports:

• whether the container exists at all

• its current state (running, exited, created, etc.)

• its healthcheck status, if the container defines one

• every port mapping it actually has configured

• if you passed an expectedPort: whether it's genuinely bound on the host right now — and if not, why (container isn't running vs. the mapping just isn't there)

check_pnpm_workspace

Given a monorepo root path, validates:

• pnpm-workspace.yaml exists and parses (via a real YAML parser, not a naive line-splitter — handles comments, multi-key files, catalogs, etc.)

• every package.json found in the tree is covered by a workspace glob pattern (catches "added a new package folder, forgot to register it")

• every glob pattern in the workspace file actually matches something (catches typos and stale entries from deleted/renamed folders)

• the root package.json pins a packageManager version — this one is personal: the pnpm bug above happened because nothing pinned the version and it silently self-updated into a broken state

• whether pnpm-lock.yaml looks stale relative to the newest package.json in the workspace

diagnose_stuck_process

Given a port number, finds whatever process is bound to it and reports its PID, command name, and OS-level state — flagging D/T/Z states (uninterruptible sleep / stopped / zombie) as potentially hung.

Setup

npm install
npm run build

Test without any client (MCP Inspector)

The Inspector is a local web UI that talks to your server directly — no Claude Desktop or other host application required:

npx @modelcontextprotocol/inspector node build/index.js

Click Connect, then List Tools, then run any tool with real arguments and see the raw request/response JSON.

Note: if you're on pnpm, pnpm dlx @modelcontextprotocol/inspector may fail with Cannot find package 'commander' — that's a known phantom-dependency bug in the Inspector package itself (works fine under npx, since npm's flat node_modules papers over it; pnpm's strict isolation correctly refuses to).

Test via raw JSON-RPC (no UI)

echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"smoke-test","version":"1.0.0"}}}
{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}
{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"ping","arguments":{}}}' | node build/index.js

Connect to an MCP host (e.g. Claude Desktop)

Add to your host's MCP config (for Claude Desktop: ~/.config/Claude/claude_desktop_config.json on Linux):

{
  "mcpServers": {
    "devenv-doctor": {
      "command": "node",
      "args": ["/absolute/path/to/devenv-doctor-mcp/build/index.js"]
    }
  }
}

Fully restart the host app afterward.

Deployment

This server supports two transports:

• stdio (default) — for local use, spawned as a subprocess by a host app (MCP Inspector, Claude Desktop, NitroStack Studio pointed at the project folder). This is what all the testing instructions above use.

• Streamable HTTP — for hosted/cloud deployment (e.g. NitroCloud), automatically enabled when a PORT environment variable is set:

PORT=3000 node build/index.js
# MCP endpoint: POST http://localhost:3000/mcp

Runs in stateless mode (no session tracking) since every tool call here is independent — nothing needs to persist between requests.

Known limitations

Being upfront about these rather than letting them surprise you:

• Glob matching doesn't support negation patterns (!**/test/**), which some pnpm-workspace.yaml files use to exclude folders. A workspace using negation may get spurious "dead pattern" warnings.

• Lockfile staleness is a mtime heuristic, and git clone resets file mtimes to roughly the same moment — so this check can false-positive immediately after a fresh clone, even on a perfectly healthy workspace.

• ps flags used in diagnose_stuck_process are GNU/Linux-specific (--no-headers); this tool hasn't been tested on macOS/BSD ps.

• Stuck-process detection is a single snapshot, not a trend — a process briefly in uninterruptible-sleep (D) state doing normal disk I/O can be flagged even though it's healthy. A more robust version would sample twice with a delay before flagging.

None of these are silent — each one is either surfaced as a message from the tool itself, or documented here.

Built with

• @modelcontextprotocol/sdk v1.29.0 (stable — the v2 rewrite wasn't released yet at time of building)

• TypeScript, Zod for input validation, yaml for real YAML parsing

• Node's child_process.execFile throughout (never exec) — every shell call uses array arguments, not interpolated strings, so user-supplied input (container names, paths) can't be used for shell injection

License

MIT