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is_rom_loaded

Verify if a ROM is loaded in the GameBoy emulator using the MCP GameBoy Server to ensure proper game initialization and control.

Instructions

Check if a ROM is currently loaded in the emulator

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • src/tools.ts:80-103 (registration)
    Registration and inline handler for the 'is_rom_loaded' MCP tool. Executes the tool logic by checking emulatorService.isRomLoaded() and returning JSON response with loaded status and ROM path.
    server.tool(
      'is_rom_loaded',
      'Check if a ROM is currently loaded in the emulator',
      {},
      async (): Promise<CallToolResult> => {
        const isLoaded = emulatorService.isRomLoaded();
        const romPath = emulatorService.getRomPath();
        
        const responseText: TextContent = {
          type: 'text',
          text: JSON.stringify({
            romLoaded: isLoaded,
            romPath: romPath || null
          })
        };
        
        log.verbose('Checked ROM loaded status', JSON.stringify({ 
          romLoaded: isLoaded, 
          romPath: romPath || null 
        }));
        
        return { content: [responseText] };
      }
    );
  • Helper method in EmulatorService that delegates the ROM loaded check to the underlying GameBoyEmulator instance.
    isRomLoaded(): boolean {
      return this.emulator.isRomLoaded();
    }
  • Core implementation in GameBoyEmulator class that returns the internal romLoaded boolean flag set upon successful ROM loading.
    public isRomLoaded(): boolean {
      return this.romLoaded;
    }
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 of behavioral disclosure. It clearly indicates a read-only check operation ('Check if a ROM is currently loaded'), which implies non-destructive behavior. However, it lacks details on return values (e.g., boolean or status message), error conditions, or dependencies on other tools like 'load_rom'. No contradiction with annotations exists since none are provided.

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 a single, clear sentence that efficiently conveys the tool's purpose without any wasted words. It is front-loaded with the core action ('Check'), making it easy to understand at a glance. Every part of the sentence earns its place by specifying the action and target.

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 tool's simplicity (0 parameters, no annotations, no output schema), the description is adequate but has gaps. It explains what the tool does but does not cover behavioral aspects like return format or error handling. For a read-only check tool, this is minimally viable, but additional context on output would improve completeness.

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?

The tool has 0 parameters, and the input schema has 100% description coverage (though empty). The description does not need to compensate for any parameter gaps. It appropriately focuses on the tool's function without unnecessary parameter details, aligning with the baseline for zero parameters.

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 tool's purpose with a specific verb ('Check') and resource ('ROM'), making it immediately understandable. It distinguishes from siblings like 'load_rom' (which loads ROMs) and 'list_roms' (which lists available ROMs), though it doesn't explicitly differentiate from all siblings. The purpose is not vague or tautological.

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 in the context of checking ROM status in an emulator, but it does not provide explicit guidance on when to use this tool versus alternatives. For example, it doesn't specify if this should be used before loading a ROM or to verify a successful load. No misleading information is present, but the guidance is limited to implied context.

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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