mgba_run_lua · mGBA MCP Server MCP: Risk & Policy

WHAT IT DOES

What mgba_run_lua does on mGBA MCP Server

AI agents invoke mgba_run_lua to trigger actions in mGBA MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why mgba_run_lua needs a policy

This is an Execute category tool because it triggers arbitrary code execution via Lua scripts. The high severity stems from the broad capabilities available to executed scripts: memory manipulation (read8/write8), I/O operations (screenshot), and callback hooks allow an AI agent to modify game state, extract sensitive game data, or cause unexpected emulator behavior.

From the tool's definition Tool allows execution of arbitrary custom Lua scripts within the emulator environment with access to memory read/write functions (emu:read8(), emu:write8()), screenshot capture (emu:screenshot()), and callback registration (callbacks:add()).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mgba_run_lua Rate-limited

mgba_run_lua stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "mgba_run_lua": {
      "limits": [
        {
          "counter": "mgba_run_lua_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches mGBA MCP Server, so you can run agents against it safely.

FAQ

Questions about mgba_run_lua

What does the mgba_run_lua tool do? +

Run a custom Lua script in the emulator. The script can use emu:read8(), emu:write8(), emu:screenshot(), callbacks:add(), etc. It is categorised as a Execute tool in the mGBA MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on mgba_run_lua? +

Register the mGBA MCP Server MCP server in PolicyLayer and add a rule for mgba_run_lua: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches mGBA MCP Server. Nothing to install.

What risk level is mgba_run_lua? +

mgba_run_lua is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit mgba_run_lua? +

Yes. Add a rate_limit block to the mgba_run_lua rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block mgba_run_lua completely? +

Set action: deny in the PolicyLayer policy for mgba_run_lua. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides mgba_run_lua? +

mgba_run_lua is provided by the mGBA MCP Server MCP server (struktured-labs/mgba-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.