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.

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