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bizhawk_reset

Reset emulated console to boot state, clearing RAM, CPU, framecount, and joypad. Use to start fresh from boot without reloading the ROM.

Instructions

PURPOSE: Reset the loaded core — equivalent to a hard reset (power cycle) of the emulated console. USAGE: Use to start fresh from boot. To return to a specific known-good point instead of boot, use bizhawk_load_state with a previously saved state file. BEHAVIOR: DESTRUCTIVE: RAM contents become indeterminate (typically zeroed), CPU returns to the reset vector, framecount resets to 0, joypad state clears, and any in-progress audio/video state is discarded. The loaded ROM stays loaded — only volatile state is cleared. Unsaved game progress is lost. Returns an error if the loaded core doesn't expose client.reboot_core — check capabilities.reboot_core in bizhawk_get_info first. RETURNS: Single line 'Core reset'.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • src/tools.ts:413-421 (registration)
    Tool definition/registration for 'bizhawk_reset', including its name, description, and empty inputSchema.
    {
      name: "bizhawk_reset",
      description:
        "PURPOSE: Reset the loaded core — equivalent to a hard reset (power cycle) of the emulated console. " +
        "USAGE: Use to start fresh from boot. To return to a specific known-good point instead of boot, use bizhawk_load_state with a previously saved state file. " +
        "BEHAVIOR: DESTRUCTIVE: RAM contents become indeterminate (typically zeroed), CPU returns to the reset vector, framecount resets to 0, joypad state clears, and any in-progress audio/video state is discarded. The loaded ROM stays loaded — only volatile state is cleared. Unsaved game progress is lost. Returns an error if the loaded core doesn't expose client.reboot_core — check `capabilities.reboot_core` in bizhawk_get_info first. " +
        "RETURNS: Single line 'Core reset'.",
      inputSchema: { type: "object", properties: {} },
    },
  • Handler case for 'bizhawk_reset' — calls bh.call('reset') and returns 'Core reset' on success.
    case "bizhawk_reset":         await bh.call("reset");          return ok("Core reset");
  • The BizhawkServer.call() method that enqueues an RPC command and returns a promise. The handler's bh.call('reset') delegates to this, which sends a JSON-RPC command over TCP to the BizHawk Lua bridge.
    async call<T = unknown>(method: string, params: Record<string, unknown> = {}): Promise<T> {
      return new Promise<T>((resolve, reject) => {
        const id = this.nextId++;
        const pending: PendingCmd = {
          id,
          method,
          params,
          resolve: (r) => resolve(r as T),
          reject,
        };
    
        const timer = setTimeout(() => {
          // Drop from queue if still waiting; from inflight if already sent.
          this.queue   = this.queue.filter((p) => p.id !== id);
          this.inflight.delete(id);
          if (this.inflight.size === 0) this.awaitingResult = false;
          reject(new Error(
            `BizHawk call "${method}" timed out (${this.timeoutMs}ms) — ` +
            `is the bridge.lua script still polling?`,
          ));
        }, this.timeoutMs);
    
        // Wrap so the timer always clears
        const origResolve = pending.resolve, origReject = pending.reject;
        pending.resolve = (r) => { clearTimeout(timer); origResolve(r); };
        pending.reject  = (e) => { clearTimeout(timer); origReject(e); };
    
        this.queue.push(pending);
      });
    }
Behavior5/5

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

Since no annotations are provided, the description fully discloses the destructive behavior, detailing exactly what changes: RAM contents become indeterminate, CPU resets, framecount resets, joypad clears, audio/video state discarded. It also notes that the ROM stays loaded and unsaved progress is lost, and mentions error conditions if the core lacks reboot_core.

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 sections (PURPOSE, USAGE, BEHAVIOR, RETURNS) and is concise, with each sentence adding value. No extraneous text.

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 complexity and lack of output schema, the description covers all necessary aspects: purpose, usage, behavioral details, return value, and error handling. It is complete for an agent to understand and use the tool correctly.

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?

The input schema has no parameters (100% coverage), so the description does not need to add parameter information. The baseline of 3 is appropriate as it does not contribute additional parameter semantics beyond what the schema already provides.

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 clearly states the tool's purpose: 'Reset the loaded core — equivalent to a hard reset (power cycle) of the emulated console.' It distinguishes itself from the sibling tool bizhawk_load_state, which is used for 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 provides explicit usage guidelines: 'Use to start fresh from boot.' It also tells when not to use it and suggests an alternative: 'To return to a specific known-good point instead of boot, use bizhawk_load_state with a previously saved state file.'

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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