horizOn MCP Server

MCP server for horizOn Backend-as-a-Service

Gives AI coding assistants documentation, live API tools, and workflow prompts for game and app development.

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Quick Install

Add to your MCP client configuration (Claude Desktop, Cursor, etc.):

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

Features

Resources (18 docs)

Documentation resources are served directly from the MCP server. No API key required.

URI	Description
horizon://overview	What is horizOn, core concepts (Account vs User), features, tier system, API structure, and SDKs
horizon://docs/auth	Authentication methods (Anonymous, Email, Google), endpoints, SDK code examples, and common errors
horizon://docs/leaderboard	Leaderboard score submission, top entries, user rank, entries around user, player profile per entry, validated only boards, with SDK examples
horizon://docs/cloud-save	Cloud save/load for JSON and binary data, tier size limits, SDK examples
horizon://docs/remote-config	Server-side key-value configuration: feature flags, game balance, A/B testing. SDK examples
horizon://docs/localization	Server-side localized strings across 15 languages: per-key translations, single/all fetch, available languages. SDK examples
horizon://docs/news	In-game news and announcements with language filtering. SDK examples
horizon://docs/gift-codes	Gift code validation and redemption for promotional rewards, including cosmetic unlocks via grants. SDK examples
horizon://docs/player-profile	Player avatar, frame and badges from a per-project cosmetics catalog, unlocks via gift code grants, profile in leaderboard entries. SDK examples
horizon://docs/validated-actions	Server-checked runs: single-use run tickets with a server seed, SHA-256 input log hash, server-only rules, validated only leaderboards, server-owned player state, start context, evidence upload, admin evidence review with sus packages and package export, rejection codes. SDK examples
horizon://docs/feedback	Bug reports, feature requests, and general feedback submission. SDK examples
horizon://docs/user-logs	Server-side event and error tracking. Requires BASIC tier or higher. SDK examples
horizon://docs/crash-reporting	Crash report submission, session tracking, fingerprinting, breadcrumbs, and auto-regression detection. SDK examples
horizon://docs/email-sending	Transactional and event-based email delivery to registered users. Templates, scheduling, status tracking, and SMTP integration. SDK examples
horizon://api/reference	Complete API reference for all horizOn App API endpoints with request/response schemas
horizon://quickstart/godot	Step-by-step guide to integrate horizOn in Godot with GDScript examples
horizon://quickstart/unity	Step-by-step guide to integrate horizOn in Unity with C# examples
horizon://quickstart/unreal	Step-by-step guide to integrate horizOn in Unreal Engine 5.5+ with the official horizOn SDK plugin. C++ and Blueprint examples

Tools (34 tools)

Live API tools that call the horizOn backend. Requires a valid API key.

horizon_submit_score, horizon_save_cloud_data, horizon_load_cloud_data, horizon_redeem_gift_code, horizon_get_profile, horizon_set_profile, horizon_start_run, horizon_submit_validated, horizon_get_state and horizon_upload_evidence also need the player's session: sign in first and pass the returned accessToken as sessionToken.

Every tool declares MCP annotations (readOnlyHint, destructiveHint, idempotentHint, openWorldHint), so clients can tell reads from writes. Destructive tools are horizon_save_cloud_data (replaces the save), horizon_set_profile (replaces the whole profile), horizon_submit_validated (consumes the ticket, can spend balances) and horizon_cancel_email. The read tools that return an object also declare an outputSchema and return structuredContent next to the JSON text. Each description names when to use the tool, which sibling to use instead, what it returns and how to recover from its errors.

Tool	Description
horizon_test_connection	Test connection to the horizOn API (health check)
horizon_signup_anonymous	Create a new anonymous user account
horizon_signup_email	Create a new user account with email and password
horizon_signin_email	Sign in with email and password
horizon_signin_anonymous	Sign in with an anonymous token
horizon_check_auth	Check whether a user session is still valid
horizon_list_leaderboards	List available leaderboard boards for multi-board calls
horizon_submit_score	Submit a score to the leaderboard (403 VALIDATED_SUBMIT_REQUIRED on validated only boards)
horizon_get_leaderboard_top	Get the top leaderboard entries with each player's profile, optionally by board key
horizon_get_user_rank	Get a user's leaderboard rank, optionally by board key
horizon_get_leaderboard_around	Get leaderboard entries around a user's position, optionally by board key
horizon_save_cloud_data	Save cloud data for a user
horizon_load_cloud_data	Load cloud save data for a user
horizon_get_remote_config	Get a single remote config value by key
horizon_get_all_remote_configs	Get all remote config values
horizon_get_localization	Get a single localized string by key, optionally for a specific language
horizon_get_all_localizations	Get all localized strings, optionally for a specific language
horizon_get_localization_languages	List the languages that have localizations for the app
horizon_get_news	Get news articles with optional language filtering
horizon_validate_gift_code	Validate a gift code without redeeming it
horizon_redeem_gift_code	Redeem a gift code for a user (returns grantedUnlocks for codes with cosmetic grants)
horizon_get_profile	Get a player's profile (avatar, frame, badges), unlocks and the cosmetics catalog
horizon_set_profile	Replace a player's whole profile (avatar, frame, up to 3 badges)
horizon_start_run	Start a server-checked run: single-use ticket with a server seed, optionally bound to a board and with a start context (game, content, simulation and replay format versions, content digest, initial state as base64)
horizon_submit_validated	Submit a run result with the ticket and the SHA-256 input log hash (given, or computed locally from base64 bytes or text), optionally with earned server-owned values; returns sus (accepted but over a soft threshold); rejections name their code
horizon_get_state	Read the player's server-owned values (balance, earned today, daily cap per value key); read only
horizon_upload_evidence	Upload the input log (text or base64, encoded locally) of a run whose submit result asked for evidence; rejections name their code
horizon_submit_feedback	Submit user feedback (bug reports, feature requests)
horizon_create_log	Create a server-side log entry (INFO, WARN, ERROR)
horizon_create_crash_report	Submit a crash report (grouped by fingerprint, with regression detection)
horizon_create_crash_session	Register a game session for the crash-free rate
horizon_send_email	Send a transactional email to a registered user from a template
horizon_cancel_email	Cancel a pending or scheduled email
horizon_get_email_status	Get the status of a sent or scheduled email

Prompts (4 prompts)

Workflow prompts that guide AI assistants through common horizOn tasks.

Prompt	Description
integrate-feature	Generate integration code for a specific horizOn feature in your game engine
setup-auth	Step-by-step guide to set up horizOn authentication in your project
debug-connection	Diagnose and fix horizOn connection issues
explain-feature	Get a detailed explanation of any horizOn feature

Configuration

Variable	Required	Description
HORIZON_API_KEY	Yes (for tools)	Your horizOn API key. Get one at horizon.pm
HORIZON_BASE_URL	No	API base URL. Defaults to https://horizon.pm

Resources (documentation) work without an API key. Only the live API tools require authentication.

Admin Tools (v1.2+)

With an Account Key (creatable in your horizOn Dashboard -> API Keys -> Create -> Account Key), the MCP server exposes additional tools that let Claude manage your dashboard -- projects, remote config, news, email templates, gift codes, users, leaderboards, cloud-save data, crash reports, feedback, user logs, SMTP, and Validated Actions (rules, runs, player values and the evidence review).

How to get your Account Key

1. Log in to your horizOn Dashboard
2. Navigate to API Keys in the sidebar
3. Click Create API Key
4. Select Account Key as the key type
5. Choose whether the key can access the entire account, a single Project API Key, or selected feature groups
6. Click Create -- your key will be shown once. Copy it immediately.
7. Add the key to your MCP configuration (see Setup below)

Setup

Add both keys to your MCP client configuration:

{
  "mcpServers": {
    "horizOn": {
      "command": "npx",
      "args": ["-y", "horizon-mcp"],
      "env": {
        "HORIZON_API_KEY": "your-project-key (for player-facing tools)",
        "HORIZON_ACCOUNT_API_KEY": "your-account-key (for dashboard tools)"
      }
    }
  }
}

Both can be set together or individually. Admin tools only register when the account key is set -- otherwise the server exposes only the original player-facing tools.

Scope

Account Keys inherit your account's tier (FREE/BASIC/PRO/ENTERPRISE) -- they grant no extra privileges. A key can be full-account, limited to a single Project API Key, limited to selected feature groups, or both. Platform-admin-only endpoints (Blog, Banner, System-Config) are automatically unreachable. A handful of ultra-sensitive endpoints (account deletion, credentials change, key management itself, subscription cancel) require a dashboard session and cannot be called via an Account Key.

When a key is project-scoped, the backend enforces that scope on direct HTTP calls too. Account-wide endpoints or ID-only endpoints that cannot prove project context are rejected for project-scoped keys.

Tool Groups

Admin tools carry the same annotations as the player tools: list, get and statistics tools are read only, update and delete tools are marked destructive.

Prefix	Description
horizon_admin_projects_*	Project API key management (create/update/regenerate/revoke/delete)
horizon_admin_remoteconfig_*	Remote config CRUD
horizon_admin_news_*	Multilingual news (titles/messages as {lang: content})
horizon_admin_emailtemplates_*	Multilingual email templates with variables
horizon_admin_giftcodes_*	Gift code CRUD + revoke
horizon_admin_users_*	User management + statistics (no full-list needed)
horizon_admin_leaderboard_*	Leaderboard entries + statistics
horizon_admin_cloudsave_*	Cloud save data + statistics
horizon_admin_crashes_*	Crash groups, reports, statistics
horizon_admin_feedback_*	Read user feedback
horizon_admin_userlogs_*	Read user logs
horizon_admin_smtp_*	Account SMTP configuration (password always returned masked)
horizon_admin_validated_evidence_*	Validated Actions evidence review: list (top N records or, with sus: true, sus packages), quota, metadata (with susPackage), log download (base64 or hashes only), package export (ZIP written to a local file, with the integrity headers), delete
horizon_admin_validated_rules_*, _usage_get, _runs_list, _state_*	Validated Actions configuration: rule set per Project API key (get, replace, delete), run capacity of the hour, recent runs with rejection codes (filter sus), server-owned player values (read, support correction)

What is horizOn?

horizOn is a multi-tenant Backend-as-a-Service platform built for game and app developers. It provides a managed backend so developers can focus on building their game or app instead of server infrastructure.

Core features:

• Authentication (Anonymous, Email, Google, Apple)
• Leaderboards
• Cloud Save
• Remote Config
• Localization
• News and Announcements
• Gift Codes
• Player Profile (avatar, frame, badges)
• Validated Actions (server-checked runs, validated only leaderboards, server-owned currency)
• User Feedback
• User Logs
• Crash Reporting
• Email Sending

Learn more at horizon.pm. Install this MCP server via npm.

Supported Engines

• Godot 4.5+ -- GDScript SDK
• Unity 6 -- C# SDK
• Unreal Engine 5.5+ -- C++ and Blueprint SDK

Development

# Clone the repository
git clone https://github.com/ProjectMakersDE/horizOn-mcp.git
cd horizOn-mcp

# Install dependencies
npm install

# Start the server (development mode)
npm run dev

# Build for production
npm run build

# Run tests
npm test

License

MIT