Blue Prince MCP

The Blue Prince MCP server is a purpose‑built companion for players of the indie adventure game Blue Prince. It tackles the classic dilemma of balancing helpful context with preserving the surprise‑driven experience that defines the game. By acting as a “spoiler shield,” the server lets players keep a personal, structured vault of notes while ensuring that any external information surfaced by an AI assistant is strictly filtered to content the player has already discovered. This protects the game’s narrative integrity without sacrificing the convenience of AI‑powered assistance.

At its core, the server implements the Model Context Protocol to expose a set of tools that mirror everyday note‑taking workflows. Users can list, create, read, and update markdown notes stored in a local directory that is fully compatible with Obsidian. Each note is automatically categorized into predefined buckets—people, puzzles, rooms, items, lore, and general—and enriched with metadata. The tool set is intentionally lightweight yet powerful: gives an overview of the vault, enforces structure and spoiler rules, retrieves full content with tags, and lets players refine their entries. Future additions such as deletion or screenshot analysis are already outlined, ensuring the system can grow with player needs.

The standout feature is the built‑in spoiler‑aware protection system. It combines client‑side filtering rules, server‑side validation of content creation, and consent prompts before any potentially revealing external data is shared. Dynamic spoiler‑prevention rules are exposed as MCP resources, allowing the AI client to automatically check against the player’s documented discoveries. This layered approach guarantees that the assistant never offers information about a puzzle or plot point the player has not yet encountered, preserving the sense of discovery that is central to Blue Prince.

Developers building AI workflows will appreciate how seamlessly the server integrates. The MCP tools can be invoked from any compatible client—such as Claude Desktop—or wrapped into custom scripts. Because the vault is plain markdown, developers can link it to other systems (e.g., knowledge graphs or project management tools) without friction. The server’s configuration flexibility, with file‑based settings and environment variable overrides, makes it easy to deploy in both local and cloud environments.

In practice, a player might write a note about a mysterious painting, then later ask the AI: “Which rooms contain paintings?” The assistant will search only the player’s vault, return relevant notes, and avoid pulling in external descriptions that could spoil. For developers, the Blue Prince MCP serves as a template for any game‑centric or experience‑driven application that requires a balance between AI assistance and spoiler protection, offering a robust, extensible foundation for building engaging, discovery‑preserving AI companions.