MCP server

Let AI assistants inspect and modify the running game through the Model Context Protocol.

The runtime includes an HTTP-based Model Context Protocol server. It runs inside the game process and lets AI assistants find actors, read and write properties, and call functions at runtime. Unlocky uses it, and you can connect other MCP clients too.

Connection

The server starts automatically on port 3001 when the runtime initializes, as long as enable_mcp is true in uloader.ini. UnlockedKit enables it on install.

Endpoint	Purpose
`http://127.0.0.1:3001/mcp`	Streamable HTTP MCP endpoint
`http://127.0.0.1:3001/health`	Health check

Claude Code

Add the server to your Claude Code MCP settings:

.mcp.json

{
  "mcpServers": {
    "unreal-engine": {
      "type": "streamable-http",
      "url": "http://localhost:3001/mcp"
    }
  }
}

Tools

Actor discovery

Tool	Description
`find_actors`	Search for actors by name, label, or class.
`inspect_actor`	Get an overview of an actor: properties, components, and functions.
`get_components`	List all components on an actor.

Property editing

Property access is reflection-driven, so anything the engine exposes is available.

Tool	Description
`list_properties`	List all properties on an actor or component.
`get_property`	Read a property value. Names are matched fuzzily.
`set_property`	Write a property value.

Function calling

Tool	Description
`list_functions`	List callable functions on an actor or component.
`call_function`	Call a function through `ProcessEvent`, returning its return value and named out parameters.

Examples

Set the player's walk speed:

{"method": "tools/call", "params": {"name": "set_property", "arguments": {"actor": "Character", "property": "MaxWalkSpeed", "component": "CharacterMovement", "value": 500}}}

Find every character:

{"method": "tools/call", "params": {"name": "find_actors", "arguments": {"class": "Character"}}}

Call a Blueprint function with parameters:

{"method": "tools/call", "params": {"name": "call_function", "arguments": {"actor": "BP_Player_C", "function": "SetMaxInventorySlots", "params": {"Slots": 900}}}}

Notes

Every UObject access is dispatched to the game thread with a 5-second timeout, so tool calls never touch engine state from another thread.
The server only listens on the local machine.
MCP is not used to run Lua. Scripts are sent over the local named pipe by UnlockedKit.

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