Unreal MCP auto-detection walkthrough

MCP and agent tools · Connected applications · Unreal operations · MCP architecture

This walkthrough uses a Goblin Siege-style Unreal Engine 5.8 project as a practical test of MCP auto-detection. The same pattern applies to another Unreal project with a repository-level .mcp.json, an Epic MCP endpoint, and an optional local proxy server.

The example contains three different services:

unreal is Epic's HTTP MCP server at http://127.0.0.1:8000/mcp. Project plugins such as VibeUE can register additional tools in the same Unreal tool registry.
monolith is a local stdio proxy executable that forwards requests to an in-editor server on port 9316.
Yarin is a plugin-owned in-editor agent on port 8890. Tech Connector reports it as host evidence but does not add it to the client configuration automatically.

The names and paths below are examples. Do not assume that a detected definition is live, trusted, or portable to another computer.

Before the first connection

Install Tech Connector and sign in.
Set the primary or optional project folder to the Unreal project, for example D:\goblinRaid\GoblinSiege 5.8.
Open the project in Unreal Engine 5.8.
Enable Epic's Model Context Protocol plugin and the project plugins that provide the intended tools. Restart Unreal after enabling a plugin.
Wait for the project and its initial map to finish loading before starting the MCP-routed chat.

Full live reproduction requires the relevant Unreal plugins. Repository detection, Claude policy inspection, and missing-command reporting work without a running editor.

Repository layout and upward discovery

An MCP configuration can live above the selected Unreal project folder:

D:\goblinRaid\
  .git\
  .mcp.json
  .claude\settings.local.json
  GoblinSiege 5.8\
    GoblinSiege.uproject
    .claude\settings.local.json
    Config\DefaultEditorPerProjectUserSettings.ini
    Plugins\
    Saved\Config\WindowsEditor\EditorPerProjectUserSettings.ini
    Tools\ue_python.py

Tech Connector walks upward from the selected project folder to the nearest repository root. It does not continue searching unrelated parent folders above that boundary.

A representative .mcp.json is:

{
  "mcpServers": {
    "unreal": {
      "type": "http",
      "url": "http://127.0.0.1:8000/mcp"
    },
    "monolith": {
      "command": "D:\\goblinRaid\\GoblinSiege 5.8\\Plugins\\Monolith\\Binaries\\monolith_proxy.exe",
      "args": []
    }
  }
}

Paths with spaces are supported when the JSON is valid. An absolute command path is machine-specific: after cloning to another location, update the Monolith command to the executable on that computer.

Verify the Unreal-side settings

Epic MCP settings normally appear in the project editor settings file:

[/Script/ModelContextProtocolEngine.ModelContextProtocolSettings]
ServerUrlPath=/mcp
ServerPortNumber=8000
bAutoStartServer=True
bEnableToolSearch=True

Monolith normally listens on port 9316 while the Unreal editor is running. Its monolith_proxy.exe can be absent from a fresh clone because plugin binaries are commonly excluded from source control. Tech Connector reports that case as a missing dependency instead of attempting to run the invalid command.

Yarin may store McpServerPort=8890 in the per-user Saved/Config settings. Because that server belongs to Yarin's own agent workflow and is not declared in .mcp.json, Tech Connector reports it without silently adding or starting it.

Detect the setup in Tech Connector

Open File > Settings.
Find Source & Runtime.
Leave Use MCPs from other apps enabled.
Choose MCP Servers.
In MCP and Agent Tools, leave Automatically use detected MCP servers enabled.
Choose Refresh.

The detected summary can report:

the repository-root .mcp.json even though the selected folder is one level lower;
the declared unreal and monolith servers;
a missing Monolith proxy command;
Claude's enableAllProjectMcpServers and enabledMcpjsonServers policy resolution;
Epic MCP, Monolith, and Yarin ports found in Unreal settings;
Tools\ue_python.py as an available fallback.

Automatic detection creates a temporary runtime overlay and leaves the source .mcp.json and Claude settings unchanged. Import selected is optional; use it only when a durable copy in Tech Connector's managed configuration is desired.

Connect and verify

For the most predictable first demonstration, open Unreal before starting the MCP-routed chat. Epic's endpoint requires an MCP initialization handshake and a returned Mcp-Session-Id on later requests. A bare browser request to / or /mcp is not a valid health test.

In System Status, right-click the Unreal card.
Choose Connect to MCP.
Select unreal for Epic MCP and registered VibeUE tools, or select monolith for its proxy-backed tools.
Wait for Connecting to MCP to change to a ready status.
Right-click the connected Unreal card and choose View MCP capabilities... to inspect the combined inventory.
Start with a read-only prompt and inspect the reported project or editor state.

Useful prompts include:

Show the loaded Unreal level and selected actors. Do not change anything.
Discover the available Unreal Python subsystems.
List the Unreal MCP tools and explain which provider owns each one.
Check Monolith status and list its Blueprint, AI, behavior tree, GAS, and UI query namespaces.
Plan a point light near the selected actor, but show the proposed operation before executing it.

A ready capability inventory proves that the session and tool discovery succeeded. A scene mutation is complete only after the target actor, asset, or property is inspected in Unreal.

Expected states and recovery

Editor closed: definitions remain detected, while live Unreal endpoints are offline.
Editor busy: a short probe can report busy or slow. Do not treat one timeout as proof that the server is absent.
Monolith proxy missing: update or build the plugin binary, then correct the absolute command path and refresh.
Unreal opened after the chat started: restart the routed chat. Monolith may reconnect through its proxy, while Epic MCP can require a new session.
Epic MCP session cannot attach: use the detected Tools\ue_python.py helper as an explicit fallback when the project provides it. Tech Connector reports the helper but does not silently replace the configured server.
Yarin detected: leave it report-only unless the plugin's documentation explicitly says an external MCP client should connect to it.
Claude allow-list appears narrower than enable-all: Tech Connector reports both settings and their effective resolution instead of guessing from the allow-list alone.

What automatic detection does not do

Auto-detection does not install Unreal Engine, compile missing plugin binaries, enable proprietary plugins, rewrite absolute paths, or grant mutation permission. It also does not generically evaluate a proprietary Blueprint, Niagara, AI, or gameplay graph outside the connected host. Those operations remain subject to the server's tools, Tech Connector approvals, and live Unreal verification.

Screenshots show actual Tech Connector widgets with sample labels. A screenshot or saved graph does not prove a live DCC run.