mcp-mgba

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mgba_reset

Reset the Game Boy Advance emulator's loaded ROM, clearing all volatile state and returning to boot. Unsaved in-game progress is lost.

Instructions

PURPOSE: Reset the loaded ROM — equivalent to pressing the reset button on the GBA / Game Boy. USAGE: Use to start fresh from boot. To return to a specific known-good point instead of boot, use mgba_load_state with a previously saved slot or .ss0/.ss1/etc state file. BEHAVIOR: DESTRUCTIVE: RAM contents become indeterminate (typically the BIOS-zeroed state), CPU returns to the reset vector, frame count resets to 0, input queue clears, and any in-progress audio/video state is discarded. The loaded ROM stays loaded — only volatile state is cleared. UNSAVED IN-GAME PROGRESS IS LOST (anything not committed to cartridge SRAM via the game's save menu, and anything not snapshotted via mgba_save_state). This method is build-dependent on mGBA; check capabilities.reset in mgba_get_info first. Returns an error if the capability is missing on this build. RETURNS: Single line 'ROM reset'.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "mgba_reset"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0May 14, 2026

TDQS

A4.9/5.0

Behavior5/5

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

With no annotations provided, the description fully discloses destructive behavior: RAM indeterminate, CPU reset, frame count reset, input queue clear, audio/video discard, unsaved progress loss, build-dependency, and error handling. This exceeds the burden.

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 well-structured with labeled 'PURPOSE', 'USAGE', 'BEHAVIOR', 'RETURNS' sections, front-loads the purpose, and every sentence provides necessary information without redundancy.

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

Completeness5/5

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

Given the tool's destructive nature and lack of annotations or output schema, the description covers all critical aspects: purpose, usage guidance, behavioral details, return value, error conditions, and prerequisites.

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

Parameters4/5

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

Input schema has zero parameters with 100% coverage, so baseline is 4. The description adds no parameter details but explains the operation's effects, which is valuable context beyond the schema.

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

Purpose5/5

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

The description explicitly states 'Reset the loaded ROM — equivalent to pressing the reset button on the GBA / Game Boy.', providing a specific verb and resource. It distinguishes from sibling mgba_load_state by contrasting with returning to a saved state.

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

Usage Guidelines5/5

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

The description directly advises when to use ('start fresh from boot') and when to use an alternative ('use mgba_load_state for a saved point'), naming the sibling tool explicitly.

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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