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mGBA MCP Server

mGBA MCP Server

by struktured-labs
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
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mgba_run_lua

Execute custom Lua scripts in the mGBA emulator to automate testing, analyze game data, read/write memory, capture screenshots, and generate structured output for Game Boy, GBC, and GBA ROMs.

Instructions

Run a custom Lua script in the emulator. The script can use emu:read8(), emu:write8(), emu:screenshot(), callbacks:add(), etc.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "rom_path": "<rom_path>",
      "script": "<script>"
    },
    "name": "mgba_run_lua"
  }
}

Input Schema

NameRequiredDescriptionDefault
rom_pathYesPath to the ROM file
scriptYesLua script to execute. Use emu:quit() to exit. Write JSON to 'output.json' for structured data.
savestate_pathNoOptional savestate to load
timeoutNoTimeout in seconds (default: 30)

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A3.5/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden. It discloses key behavioral traits: the tool executes Lua scripts with emulator APIs, can output JSON, and has a timeout. However, it misses details like error handling, side effects on emulator state, or performance implications, which are important for a scripting tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core purpose and efficiently lists example Lua functions and output instructions in a single, compact sentence. Every element adds value without redundancy, making it highly concise and well-structured.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of running custom scripts in an emulator, no annotations, and no output schema, the description is moderately complete. It covers basic functionality and output method but lacks details on return values, error cases, or integration with sibling tools, leaving gaps for an AI agent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema fully documents parameters like rom_path and script. The description adds minimal value beyond the schema, mentioning Lua functions and JSON output, but doesn't elaborate on parameter interactions or advanced usage, aligning with the baseline for high coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Run a custom Lua script') and the target ('in the emulator'), which is specific and actionable. It distinguishes itself from sibling tools like mgba_run by specifying Lua scripting capabilities, though it doesn't explicitly contrast with all siblings like mgba_read_memory.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage through examples of Lua functions (emu:read8(), etc.), suggesting when to use this tool for custom scripting versus simpler read operations. However, it lacks explicit guidance on when to choose this over alternatives like mgba_run or mgba_read_memory, leaving some ambiguity.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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