loenn-mcp server

loenn-mcp

A Celeste map editor for AI agents — a Model Context Protocol (MCP) server that brings full Celeste .bin map editing to Claude, GitHub Copilot, and other MCP clients, plus a standalone pcgscene CLI for scripting and CI. Read, edit, analyze, generate, and preview maps without opening Lönn.

"For AI agents" describes who talks to this server (any MCP client), not what runs inside it — every tool here is deterministic and procedural. See No AI Inside.

Works with Everest mods and maps from Lönn or Ahorn.

Contents

• Features
• Safety: backups, copies and commits
• Opening maps in Lönn
• Sprite Fusion gray-box rooms
• Summer Engine gray-box rooms
• Shared PCG core (CelPcg)
• seleCte levels
• Tool reference
• Installation & setup
• JSON round-trip & authoring
• pcgscene CLI
• Procedural generation

Features

MCP tools for complete map manipulation (full list in the tool reference), plus the pcgscene command-line tool for scripting and CI. Every write keeps a timestamped backup, maps open in Lönn are protected from MCP writes, and gray-box rooms painted in Sprite Fusion import directly.

Core Tools

Reading & Querying

• list_maps — List all .bin files
• readmapoverview — Summary of rooms, entities, triggers, stylegrounds
• read_room — Full room details (tiles, entities, triggers, decals)
• getroomtiles — Raw tile grid (FG or BG)
• readmapmetadata — Quick metadata without full read
• search_entities — Find entities by type, position, room
• search_triggers — Find triggers by type
• compare_rooms — Side-by-side room comparison

Editing

• addentity / removeentity — Place or delete entities
• updateentity / moveentity — Modify entity properties or position
• addtrigger / removetrigger — Place or delete triggers
• setroomtiles — Replace tile grid
• addroom / removeroom — Create or delete rooms
• create_map — Create new .bin file
• update_room — Modify room properties (music, dark, wind, etc.)
• clone_room — Duplicate a room
• batchaddentities — Add multiple entities at once
• resize_room — Change room dimensions

JSON & Authoring (see JSON round-trip & authoring)

• maptojson / jsontomap — Any .bin to typed JSON and back, byte-identical; refuses lossy writes
• checkauthoringjson — Resolve hand-written content: defaults filled from Lönn plugins, unknown names flagged
• mergejsoninto_map — Add entities/triggers/rooms to a map; dry-run diff + highlighted preview, map-wide unique IDs, placement checks, additions only
• runauthorscript — Run a JavaScript authoring script (js/, lucid-dream style) and merge its output

Shortened. The full README is on GitHub.