Jutsu Unreal MCP

AI coding agents handle text files well and Unreal projects badly. Blueprints, materials, levels and gameplay assets live behind editor APIs, so an agent either cannot touch them or edits them blind: it reports "done" on a Blueprint that never compiled, spends its context on oversized dumps, and has no way to see what happens in Play In Editor.

Jutsu Unreal MCP is an editor-only C++ module that runs an MCP server inside the Unreal Editor over loopback HTTP, with no Python, Node or cloud service. Eight fixed tools (context, find, inspect, apply, verify, jobs, read and capabilities) front a versioned registry of 523 editor operations on UE 5.8: Blueprints, UMG, materials, animation, Niagara, MetaSound, PCG, the Gameplay Ability System, StateTree, World Partition and more. Input and output schemas are closed, so a malformed call is refused before it touches the project, and the refusal names the expected value and the capability that would have been correct.

The hard parts were honesty and size. Every change returns a receipt with per-step outcomes and compile and save state; verification answers passed, failed or unknown with the observed value, including checks inside a Play In Editor session held open by a job. Every response is capped at 65,536 bytes by default, with explicit continuation and no silent truncation, so a large graph can be read completely without flooding the agent. One source tree builds a separate package for each of UE 5.5, 5.6, 5.7 and 5.8, guarded by per-engine contract baselines and 68 end-to-end cases that drive a live editor.

Published on Fab on August 11, 2026, ten days after the first commit. The current release, 4.0.1 (September 2026), runs on Unreal Engine 5.5 to 5.8 on Windows and is tested with Claude Code, Codex and OpenCode. Public documentation and support issues live in the JutsuUnrealMcpPublic repository on GitHub.