Steam MCP

An MCP server that gives Claude access to a Steam library: which games you own, what you have been playing, which achievements you have and have not unlocked, and how rare they are. It exists so Claude can help you hunt achievements: what is left, what is easy, what is brutal, and how to get it.

The server only returns data from the Steam Web API. Advice, priorities and guides come from Claude, which works from that data and can search the web for a specific achievement.

Security

The server has no authentication. Anyone who can reach /mcp can call its tools using your Steam API key, and /health returns your default SteamID.

It listens on all network interfaces, so keep the port firewalled. If you expose it to the internet (a tunnel, a reverse proxy), treat the URL as a secret or put access control in front of it. Never commit .env.

Related MCP server: steam-mcp

Features

• Library: every game on the account, with playtime.

• Recent games: what was played in the last 2 weeks.

• Achievements per game: locked and unlocked, names, descriptions, unlock dates.

• Rarity: the global unlock percentage of each achievement.

• Game search: find an appid by name, using a cached copy of the Steam app list.

• Profile lookup: get a SteamID64 from a nickname, a vanity URL or a profile link.

Requirements

1. Node.js 20.12 or newer.

2. A Steam Web API key, free from https://steamcommunity.com/dev/apikey. The "Domain Name" field is only a label, so localhost works. The key is permanent and tied to your account, so keep it secret.

3. A SteamID64, the 17-digit account ID. If you don't know yours, the resolve_steam_id tool finds it from a nickname or profile link.

4. A public profile. In Steam, set Privacy → "Game details" to Public. Otherwise the Web API returns neither the game list nor achievements.

Setup

npm install
npm run build
cp .env.example .env   # then fill in your values

Running

npm start     # runs dist/index.js, serving http://localhost:3846/mcp
npm run dev   # runs from source with tsx, no build step

Check that it is up:

curl -s localhost:3846/health
# {"status":"ok","hasApiKey":true,"defaultSteamId":"7656...","cache":{"entries":N}}

Environment variables are read at startup, so restart the server after editing .env.

Connecting to Claude

Claude Code:

claude mcp add --transport http steam http://localhost:3846/mcp

claude.ai: go to Settings → Connectors → Custom connector and enter your server's public URL. This requires exposing the server to the internet, so read Security first. The URL must include the /mcp path. Without it, the connector posts to /, gets a 404, assumes authorization is required, and fails with "Couldn't register…".

Tools

steam_id is always optional and falls back to STEAM_ID.

The most useful call is get_player_achievements with filter=locked and sort=rarity. It lists your remaining achievements from most common (usually easiest) to rarest.

Example prompts

• "What have I played in the last 2 weeks?"

• "Show my top 10 games by playtime."

• "Which achievements are easiest to finish in Kingdom Come: Deliverance II? Give a short guide for each."

• "How many achievements are left in Baldur's Gate 3, and which are the rarest?"

• "Find the appid for Hollow Knight and show my achievement progress."

• "Of my recent games, which one am I closest to 100% in?"

How it works

The server speaks stateless Streamable HTTP MCP, built with TypeScript, the official @modelcontextprotocol/sdk and Express. Each request gets a fresh transport with no session ID, which is what the claude.ai web connector accepts most reliably. Each tool wraps one or more Steam Web API calls and returns cleaned-up JSON.

Mapping appids to names

• Your own games need no mapping: GetOwnedGames with include_appinfo=true already returns names.

• Searching by name uses IStoreService/GetAppList/v1/. Steam removed the old keyless ISteamApps/GetAppList, which now returns 404, so this needs an API key and paginated downloads. The list is large, so it is cached on disk for 24 hours.

Hidden achievements

For hidden achievements, Steam deliberately withholds the description until you unlock them, both in GetSchemaForGame and on the community pages. Only the name, rarity and hidden flag are available. That is enough for Claude to find a guide by name. The descriptions do exist in the client's UserGameStatsSchema_<appid>.bin file, but this server doesn't read it, to avoid fragile parsing with incomplete coverage.

Project structure

src/
├── index.ts    # MCP server, tool registration, Express + Streamable HTTP
├── steam.ts    # Steam Web API client
├── format.ts   # cleans up games, merges achievements (schema + status + rarity)
└── cache.ts    # TTL cache with disk persistence

License

MIT