Monolith is a native C++ plugin that gives AI assistants read and write access to an Unreal Engine 5.7 or 5.8 project over the Model Context Protocol. Instead of registering every action as its own tool, each domain registers a single {namespace}query(action, params) dispatch tool, and a central monolithdiscover() lists what is available, so a client's tool list stays small rather than carrying more than a thousand entries. Discovery is terse by default — a name and a one-line description per action — with the full parameter schema one further call away.
Roughly 1,400 actions span more than 25 namespaces: Blueprints, Materials, Animation, Niagara, Mesh, UI including CommonUI, AI systems such as behavior trees, state trees, EQS, smart objects, perception and navigation, the Gameplay Ability System, Logic Driver state machines, ComboGraph combo trees, Audio through Sound Cues and MetaSounds, editor control including builds and log capture, engine source search across roughly 967,000 symbols offline, project asset search over SQLite FTS5, INI configuration, and level sequences.
A Reflection Intelligence layer adds query surfaces for architectural decision records, repository hotspot and co-change risk signals, Unreal Header Tool reflection edges cross-joined with the asset registry, replication inspection covering replicated classes, RPCs and OnRep handlers, read-only composer actions for pull-request review and release pre-flight, and index maintenance. Ergonomic helpers apply across every action: response shaping fields, automatic backslash rewriting on asset paths, fuzzy suggestions on dispatch errors, read-only and destructive annotations in the tool list, cursor pagination, and a proxy-side call log.
Two zero-dependency executables ship alongside the plugin: a stdio-to-HTTP proxy that keeps an assistant session alive across editor restarts, and an offline query tool that serves the source index, asset index, and Reflection Intelligence surfaces without launching the editor. The plugin listens for MCP traffic on a local HTTP port; because Unreal's HTTP server module exposes no bind-address parameter, that listener is reachable on every network interface, CORS is restricted to localhost origins, and the plugin can be disabled or firewalled on untrusted networks.
Features
- Namespace dispatch: one query tool per domain plus a discovery tool, keeping the assistant's context free of a large tool catalogue
- Blueprint and material authoring: create, compile, and inspect Blueprints and materials, including variable-reference census and contract reconciliation
- Animation authoring: AnimGraph nodes, state machines, blend spaces, motion matching, retargeting, and anim-node binding read and write
- Niagara authoring: module-stack actions, direct HLSL read and overwrite on custom nodes, and search by parameter, data interface, or material
- AI and gameplay systems: behavior trees, state trees, EQS, smart objects, perception, navigation, the Gameplay Ability System, and combo graphs
- Engine and project search: an offline index of roughly 967,000 engine symbols and a SQLite FTS5 index of project assets
- C++ authoring lookups: include paths, exact signatures, deprecation checks, symbol verification, example usage, build dependency suggestions, header lint, and class stubs
- Reflection Intelligence: decision records, risk hotspots, reflection edges, replication audits, review composers, and index rebuilds
- Live PIE control: read object properties, call functions, set control rotation, inject input actions, sample time series, and read stat groups during play-in-editor
- Standalone binaries: an MCP proxy that survives editor restarts and an offline query tool with results verified against the live server
- Client support: works with Claude Code, Cursor, Cline, or any MCP-compatible client on Windows, macOS, and Linux
