HorizOn

What the horizOn MCP server does

The horizOn MCP server connects AI coding assistants to the horizOn Backend-as-a-Service platform. It provides three MCP surfaces:

• Documentation resources for backend concepts, API endpoints, SDK usage, and engine integration.
• Live tools that call the horizOn API for authentication, player data, game services, diagnostics, and email.
• Workflow prompts for feature integration, authentication setup, connection debugging, and feature explanations.

The documentation includes quickstarts for Godot, Unity, and Unreal Engine 5.5 or later. Covered backend areas include leaderboards, cloud saves, remote configuration, localization, news, gift codes, player profiles, validated actions, feedback, logs, crash reporting, and transactional email.

How it works

An MCP client starts the package with npx -y horizon-mcp. The server exposes 18 documentation resources under horizon:// URIs, including an overview, feature-specific guides, the complete API reference, and engine quickstarts. These resources do not require an API key.

The 34 live tools use the horizOn API. Set HORIZON_API_KEY for tool access; HORIZON_BASE_URL can override the default API endpoint. Authentication tools create or validate sessions, while several player-specific operations require the returned access token as sessionToken.

Tools include MCP annotations that identify read-only, destructive, idempotent, and open-world behavior. Object-returning read tools also provide an output schema and structured content alongside JSON text. Destructive operations include replacing cloud saves, replacing a full profile, consuming a validated-run ticket, and cancelling an email.

Setup and configuration

Add the server to the MCP client configuration using the npm command and provide the API key in the environment section:

{
  "mcpServers": {
    "horizOn": {
      "command": "npx",
      "args": ["-y", "horizon-mcp"],
      "env": {
        "HORIZON_API_KEY": "your-api-key-here"
      }
    }
  }
}

The key is obtained from horizon.pm. HORIZON_BASE_URL is optional and defaults to https://horizon.pm. Documentation resources remain available without a key, but live API tools require one. Claude Desktop and Cursor are named as supported configuration targets in the project instructions.

Tools and capabilities

Authentication tools support anonymous accounts, email signup, email signin, anonymous-token signin, and session checks. Game-service tools can list boards, submit and read leaderboard data, save and load cloud data, read remote configuration, retrieve localized strings, list available languages, fetch news, and validate or redeem gift codes.

Profile tools read or replace player cosmetics data. Validated-action tools start a server-checked run, submit a result with a SHA-256 input-log hash, read server-owned values, and upload evidence when requested. A submission can report a soft-threshold sus result or a rejection code.

Additional tools submit feedback, create INFO/WARN/ERROR log entries, register crash sessions, submit crash reports with fingerprint grouping and regression detection, send templated transactional emails, cancel pending or scheduled emails, and check email status. Workflow prompts help generate engine-specific integration code, configure authentication, diagnose connections, or explain a feature.