Driving the editor

MCP server

While the editor is open, Exaro Studio serves its tools over the Model Context Protocol. Any MCP-aware assistant can read and change your project — through the same approval queue the chat panel uses.

The endpoint

URL: http://127.0.0.1:8765/mcp
Transport: Streamable HTTP, JSON-RPC 2.0, MCP protocol version 2025-06-18.
Bound to loopback, so there is no auth and nothing off-machine can reach it. It runs on its own thread and stays responsive when the editor is not the focused window.
Tools exposed: all 287 in the tool reference.

NoteRunning a second editor, or a test suite alongside your working one? Set HS_MCP_PORT in that process's environment and its server binds there instead.

Connecting a client

Claude Code

bash

claude mcp add exaro-unreal http://127.0.0.1:8765/mcp

Claude Desktop

Add to %APPDATA%\Claude\claude_desktop_config.json on Windows, or ~/Library/Application Support/Claude/claude_desktop_config.json on macOS:

json

{
  "mcpServers": {
    "exaro-unreal": { "url": "http://127.0.0.1:8765/mcp" }
  }
}

Cursor

Settings → MCP → Add new MCP server, with the same JSON as above.

Restart the client. The Exaro Studio tools show up in its tool list, and the editor world it is talking to is whatever you have open.

Verifying the connection

ex_ping is a read-only call that returns the server version and the name of the current editor world. If it answers, you are wired up:

bash

curl -s http://127.0.0.1:8765/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call",
       "params":{"name":"ex_ping","arguments":{}}}'

What an external client can and cannot do

Read-only tools — asset searches, log tails, reflection queries, screenshots — execute immediately. Every mutating tool builds a preview and blocks in the editor's approval panel until you decide. An outside agent cannot quietly rewrite your level while you are in another window.

CarefulThere is an auto-approve escape hatch (HS_MCP_AUTO_APPROVE=1, and a YOLO toggle in the panel) for scripted runs. It is off by default and it bypasses review for non-undoable writes and deletes too. Do not enable it on a project you care about.

Running next to UE 5.8's built-in server

Unreal 5.8 ships an experimental MCP server of its own on port 8000. The two coexist — different ports, different tools, and only Exaro Studio previews and approves. See the 5.8 comparison.

Chat panel

Approvals & undo