# Multiplayer Agent

> Make any game multiplayer with one key, no engineering, no code.

Multiplayer Agent is a hosted multiplayer backend for browser games. You add one script
tag and a publishable key to an HTML or JavaScript game and it becomes real-time
multiplayer, no server to write, deploy or scale. It can also be driven directly
by an AI coding agent over the Model Context Protocol, so a game can be built
without leaving the editor.

## What it does
- Real-time rooms with shared state; rooms are created on first join.
- Ownership by construction: a client can only write its own player's fields.
- Server-authoritative game logic for rules a client must not be able to fake,
  with versioning, rollback and error logs.
- Player identity (anonymous-first, optional username login) and saved progress.
- Leaderboards, scoped per game or across a studio.
- Player-created content with browsing, voting and moderation.
- Monetization through Stripe, plus bring-your-own ads id.
- First-party analytics: sessions, retention, concurrency, client errors.

## What it is not suited to
- Competitive twitch games (fast shooters, racing). The transport is reliable
  rather than UDP, and there is no client prediction or rollback.
- Native Unity or Unreal projects. The client SDK targets the browser.
- Hidden-information games by default: room state replicates to everyone in the
  room unless the secret is held in server-side logic.

## Pricing
Billed by monthly active players, not by concurrent connections. Concurrency
spikes cost nothing extra and an idle game costs nothing. Limits are measured
rather than enforced: exceeding one raises an alert, it does not drop players.
- Free: free: up to 1,000 monthly active players, 3 games, 30 concurrent players per game, 10 GB traffic
- Indie: $15/month or $150/year: up to 25,000 monthly active players, 12 games, 200 concurrent players per game, 100 GB traffic
- Pro: $59/month or $590/year: up to 75,000 monthly active players, 25 games, 800 concurrent players per game, 300 GB traffic
- Studio: $199/month or $1,990/year: up to 250,000 monthly active players, 100 games, 2,000 concurrent players per game, 1,000 GB traffic

Full details: https://multiplayeragent.com/pricing

## Documentation
- [Documentation](https://multiplayeragent.com/docs): the SDK reference, arranged by topic.
- [Full SDK reference](https://multiplayeragent.com/docs/full): the entire reference on one page.
- [Plain-text corpus](https://multiplayeragent.com/llms-full.txt): everything on this site as text.
- [FAQ](https://multiplayeragent.com/faq): limits, cost, and what to reach for when.

## Guides and comparisons
- [Looking for a Photon alternative?](https://multiplayeragent.com/compare/photon-alternative): How Multiplayer Agent compares to Photon for browser and .io games: billed by monthly players instead of concurrent connections, with no server code to write.
- [Looking for a Playroom alternative?](https://multiplayeragent.com/compare/playroom-alternative): How Multiplayer Agent compares to Playroom: the same monthly-players pricing model, plus authoritative server logic, leaderboards, saves and an agent-native build path.
- [How to choose a multiplayer backend for a browser game](https://multiplayeragent.com/compare/best-multiplayer-backend-for-browser-games): A practical guide to picking a multiplayer backend for a browser or .io game: what to compare, which pricing meter fits which game, and when to pick something else.
- [Looking for a Nakama alternative?](https://multiplayeragent.com/compare/nakama-alternative): How Multiplayer Agent compares to Nakama for browser games: no server to run or write modules for, billed by monthly players, and a much smaller job to get playable.
- [How to sync player positions between browsers](https://multiplayeragent.com/guides/sync-player-positions-between-browsers): Send your own position on a fixed tick, draw everyone else by moving toward their last known position, and movement looks smooth on an ordinary connection.
- [How to add a leaderboard to a JavaScript game](https://multiplayeragent.com/guides/add-a-leaderboard-to-a-js-game): Add a persistent leaderboard to a browser game: submit a score, read the top of the board and the player's own rank, and make the scores trustworthy.
- [How to add multiplayer to a browser game](https://multiplayeragent.com/guides/add-multiplayer-to-a-browser-game): Add real-time multiplayer to an existing HTML or JavaScript game with one script tag: sync player positions, share room state, and handle joins and leaves.
- [How to make an .io game](https://multiplayeragent.com/guides/how-to-make-an-io-game): What an .io game actually needs: a shared arena, many players in one room, fair rules and a leaderboard, and the shortest path to a playable one in the browser.
- [Make a multiplayer game with Claude Code](https://multiplayeragent.com/guides/multiplayer-game-with-claude-code): Connect Multiplayer Agent to Claude Code or any MCP-capable agent, then describe the game you want. The agent defines the room, writes the client and deploys server rules.

## Getting started
1. Sign up at https://multiplayeragent.com/login: the free tier needs no card.
2. Copy the publishable key from the dashboard.
3. Add the script tag and call MP.join with the key and a room name.

## Connecting an AI agent (Model Context Protocol)
This platform exposes a tool server, so an agent can create the game, define the
room, write the client and deploy server-side rules without a human reading an
API reference first. It is a deterministic API, not a language model.

Endpoint: https://api.multiplayeragent.com/mcp  (streamable HTTP)
Auth:     Authorization: Bearer <secret key>, starting sk_
The secret key is per studio and is shown at https://multiplayeragent.com/dashboard/key after signup.
It is NOT the publishable key that ships inside a game, and must not be pasted
into client code or shared in chat.

Config for an MCP client (for example .mcp.json in Claude Code):
{
  "mcpServers": {
    "multiplayer-agent": {
      "type": "http",
      "url": "https://api.multiplayeragent.com/mcp",
      "headers": { "Authorization": "Bearer sk_your_secret_key" }
    }
  }
}

Tools include: create_game, list_games, set_game_name, define_room_type,
get_connection_info, get_client_snippet, get_sdk_reference, deploy_room_logic,
rollback_room_logic, list_room_logic, get_room_logs, set_player_scope.
Setup page: https://multiplayeragent.com/mcp
Walkthrough: https://multiplayeragent.com/guides/multiplayer-game-with-claude-code