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mcp-ppsspp

by dmang-dev
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TypeScript
Hybrid

ppsspp_breakpoint_remove

Remove a previously-set CPU execution breakpoint by address. Idempotent operation that cleans up breakpoints during debugging.

Instructions

PURPOSE: Remove a previously-added CPU execution breakpoint. USAGE: Clean up breakpoints when done debugging. To remove all, query ppsspp_breakpoint_list first. BEHAVIOR: Modifies PPSSPP's breakpoint table. Idempotent for non-existent breakpoints (no error). RETURNS: Single line 'Breakpoint removed at ADDR_HEX'.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
addressYesPSP execution address of the breakpoint to remove.

Implementation Reference

  • src/tools.ts:597-600 (handler)
    The handler for the 'ppsspp_breakpoint_remove' tool. Calls PPSSPP's 'cpu.breakpoint.remove' RPC with the address parameter, then returns a success message.
    case "ppsspp_breakpoint_remove": {
  await pp.call("cpu.breakpoint.remove", { address: a() });
  return ok(`Breakpoint removed at ${addrHex(a())}`);
}
  • src/tools.ts:367-382 (schema)
    The tool definition (name, description, inputSchema) for 'ppsspp_breakpoint_remove'. Defines the 'address' integer parameter (minimum 0) as required.
    {
  name: "ppsspp_breakpoint_remove",
  description:
    "PURPOSE: Remove a previously-added CPU execution breakpoint. " +
    "USAGE: Clean up breakpoints when done debugging. To remove all, query ppsspp_breakpoint_list first. " +
    "BEHAVIOR: Modifies PPSSPP's breakpoint table. Idempotent for non-existent breakpoints (no error). " +
    "RETURNS: Single line 'Breakpoint removed at ADDR_HEX'.",
  inputSchema: {
    type: "object",
    required: ["address"],
    properties: {
      address: { type: "integer", minimum: 0, description: "PSP execution address of the breakpoint to remove." },
    },
    additionalProperties: false,
  },
},
  • src/tools.ts:405-613 (registration)
    The 'registerTools' function that registers all tools on the MCP server, including the switch-case that routes 'ppsspp_breakpoint_remove' to its handler. Also registers the tool list via ListToolsRequestSchema.
    export function registerTools(server: Server, pp: PpssppClient): void {
  server.setRequestHandler(ListToolsRequestSchema, async () => ({ tools: TOOLS }));

  server.setRequestHandler(CallToolRequestSchema, async (req) => {
    const { name, arguments: args = {} } = req.params;
    const p = args as Record<string, unknown>;
    const a = () => p.address as number;

    switch (name) {
      case "ppsspp_ping": {
        const r = await pp.call<{ version?: string; name?: string }>("version");
        return ok(`pong (${r.name ?? "PPSSPP"} ${r.version ?? "(unknown version)"})`);
      }

      case "ppsspp_get_info": {
        const status = await pp.call<{ game?: { id?: string; title?: string; version?: string } | null; paused?: boolean; stepping?: boolean }>("game.status");
        const lines: string[] = [];
        if (status.game) {
          lines.push(`Title:   ${status.game.title ?? "(unavailable)"}`);
          lines.push(`Disc ID: ${status.game.id ?? "(unavailable)"}`);
          lines.push(`Version: ${status.game.version ?? "(unavailable)"}`);
        } else {
          lines.push("No game loaded.");
        }
        const state = status.stepping ? "stepping (paused)" : status.paused ? "paused" : "running";
        lines.push(`State:   ${state}`);
        return ok(lines.join("\n"));
      }

      case "ppsspp_read8": {
        const r = await pp.call<{ value: number }>("memory.read_u8", { address: a() });
        return ok(`${addrHex(a())}: ${fmtHex(r.value)}`);
      }
      case "ppsspp_read16": {
        const r = await pp.call<{ value: number }>("memory.read_u16", { address: a() });
        return ok(`${addrHex(a())}: ${fmtHex(r.value)}`);
      }
      case "ppsspp_read32": {
        const r = await pp.call<{ value: number }>("memory.read_u32", { address: a() });
        return ok(`${addrHex(a())}: ${fmtHex(r.value)}`);
      }
      case "ppsspp_read_range": {
        const r = await pp.call<{ base64: string }>("memory.read", { address: a(), size: p.size });
        const bytes = Buffer.from(r.base64 ?? "", "base64");
        const hex = Array.from(bytes).map((b) => b.toString(16).padStart(2, "0").toUpperCase()).join(" ");
        return ok(`${addrHex(a())} [${bytes.length} bytes]:\n${hex}`);
      }
      case "ppsspp_read_string": {
        const r = await pp.call<{ value: string }>("memory.readString", { address: a(), type: "utf-8" });
        return ok(`${addrHex(a())}: ${JSON.stringify(r.value ?? "")}`);
      }

      case "ppsspp_write8": {
        await pp.call("memory.write_u8", { address: a(), value: p.value });
        return ok(`Wrote ${fmtHex(p.value)} → ${addrHex(a())}`);
      }
      case "ppsspp_write16": {
        await pp.call("memory.write_u16", { address: a(), value: p.value });
        return ok(`Wrote ${fmtHex(p.value)} → ${addrHex(a())}`);
      }
      case "ppsspp_write32": {
        await pp.call("memory.write_u32", { address: a(), value: p.value });
        return ok(`Wrote ${fmtHex(p.value)} → ${addrHex(a())}`);
      }
      case "ppsspp_write_range": {
        const bytes = Buffer.from(p.bytes as number[]);
        const base64 = bytes.toString("base64");
        await pp.call("memory.write", { address: a(), base64 });
        return ok(`Wrote ${bytes.length} bytes → ${addrHex(a())}`);
      }

      case "ppsspp_press_buttons": {
        await pp.call("input.buttons.send", { buttons: p.buttons });
        const pressed = Object.entries(p.buttons as Record<string, boolean>)
          .filter(([, v]) => v).map(([k]) => k);
        return ok(`Set buttons: ${pressed.length ? pressed.join("+") : "(all released)"}`);
      }
      case "ppsspp_press_button": {
        await pp.call("input.buttons.press", { button: p.button, duration: p.duration ?? 1 });
        return ok(`Pressed ${p.button} for ${p.duration ?? 1} frames (auto-released)`);
      }
      case "ppsspp_send_analog": {
        await pp.call("input.analog.send", { stick: p.stick, x: p.x, y: p.y });
        return ok(`Set analog stick ${p.stick} to (${p.x}, ${p.y})`);
      }

      case "ppsspp_pause": {
        // cpu.stepping is fire-and-forget per PPSSPP source ("No immediate
        // response. Once CPU is stepping, a 'cpu.stepping' event will be
        // sent."). Send it, then poll cpu.status until stepping=true.
        await pp.fireAndForget("cpu.stepping");
        await pp.waitForState((s) => s.stepping === true);
        return ok("Emulation paused");
      }
      case "ppsspp_resume": {
        await pp.fireAndForget("cpu.resume");
        await pp.waitForState((s) => s.stepping === false);
        return ok("Emulation resumed");
      }
      case "ppsspp_step": {
        const r = await pp.call<{ pc?: number }>("cpu.stepInto");
        return ok(`Stepped one instruction. PC: ${r.pc !== undefined ? addrHex(r.pc) : "(unknown)"}`);
      }
      case "ppsspp_reset": {
        await pp.call("game.reset");
        return ok("Game reset");
      }
      case "ppsspp_screenshot": {
        // PPSSPP's gpu.buffer.* events all require CORE_STEPPING_CPU (or GPU
        // stepping) state — they fail with "Neither CPU or GPU is stepping"
        // otherwise. We transparently pause→capture→resume so callers can
        // screenshot any time without managing pause state. If the emulator
        // was already paused, we leave it paused.
        //
        // source='render' (default) uses gpu.buffer.renderColor → reads the
        // active GPU render target. Safer: GPU_GetCurrentFramebuffer hits a
        // different code path than the crash-prone GPU_GetOutputFramebuffer.
        //
        // source='output' uses gpu.buffer.screenshot → reads the final
        // composited output (what's on screen, post scaling/shaders). Can
        // CRASH PPSSPP on some games: upstream has an `_assert_(buf != nullptr)`
        // after GPU_GetOutputFramebuffer that fires when the function returns
        // true with a null buffer (observed on some homebrew). We can't catch
        // a process abort from outside, but v0.1.2's auto-reconnect means MCP
        // recovers when PPSSPP is relaunched.
        const source = (p.source as string | undefined) ?? "render";
        const event  = source === "output" ? "gpu.buffer.screenshot" : "gpu.buffer.renderColor";
        const statusBefore = await pp.call<{ stepping?: boolean; paused?: boolean }>("cpu.status");
        const wasStepping = !!statusBefore.stepping;
        if (!wasStepping) {
          await pp.fireAndForget("cpu.stepping");
          await pp.waitForState((s) => s.stepping === true);
        }
        try {
          // type: "base64" returns the raw base64 payload; the default "uri"
          // returns a "data:image/png;base64,..." prefix which we'd have to strip.
          const r = await pp.call<{ base64?: string; uri?: string }>(event, { type: "base64" });
          let b64 = r.base64;
          if (!b64 && r.uri) {
            // Belt-and-suspenders: if PPSSPP returned a URI anyway, strip the prefix.
            const m = /^data:image\/png;base64,(.*)$/.exec(r.uri);
            if (m) b64 = m[1];
          }
          if (!b64) {
            throw new Error(`PPSSPP did not return screenshot data from ${event} (no game loaded, or framebuffer not readable?)`);
          }
          return {
            content: [
              { type: "text" as const, text: `Screenshot captured (source: ${source}, event: ${event}).` },
              { type: "image" as const, data: b64, mimeType: "image/png" },
            ],
          };
        } finally {
          if (!wasStepping) {
            try {
              await pp.fireAndForget("cpu.resume");
              await pp.waitForState((s) => s.stepping === false, { timeoutMs: 2000 });
            } catch { /* best-effort */ }
          }
        }
      }

      case "ppsspp_get_registers": {
        // PPSSPP's cpu.getAllRegs returns categories with PARALLEL arrays:
        //   { categories: [{ name, registerNames: [...], uintValues: [...], floatValues: [...] }] }
        // Not an array of {name, value} objects as I first assumed.
        const r = await pp.call<{
          categories?: Array<{
            name: string;
            registerNames?: string[];
            uintValues?: number[];
            floatValues?: string[];
          }>;
        }>("cpu.getAllRegs");
        const lines: string[] = [];
        for (const cat of r.categories ?? []) {
          lines.push(`── ${cat.name} ──`);
          const names = cat.registerNames ?? [];
          const vals  = cat.uintValues ?? [];
          for (let i = 0; i < Math.max(names.length, vals.length); i++) {
            const nm = names[i] ?? `r${i}`;
            const v  = vals[i];
            lines.push(`  ${nm.padEnd(8)} = ${v !== undefined ? addrHex(v) : "(unavailable)"}`);
          }
        }
        return ok(lines.join("\n") || "(no registers returned)");
      }

      case "ppsspp_breakpoint_add": {
        await pp.call("cpu.breakpoint.add", { address: a() });
        return ok(`Breakpoint added at ${addrHex(a())}`);
      }
      case "ppsspp_breakpoint_remove": {
        await pp.call("cpu.breakpoint.remove", { address: a() });
        return ok(`Breakpoint removed at ${addrHex(a())}`);
      }
      case "ppsspp_breakpoint_list": {
        const r = await pp.call<{ breakpoints?: Array<{ address: number; enabled?: boolean; condition?: string }> }>("cpu.breakpoint.list");
        const bps = r.breakpoints ?? [];
        if (bps.length === 0) return ok("No breakpoints set.");
        const lines = bps.map((b) => `  ${addrHex(b.address)} ${b.enabled === false ? "(disabled)" : ""}${b.condition ? ` if ${b.condition}` : ""}`);
        return ok(`${bps.length} breakpoint${bps.length === 1 ? "" : "s"}:\n${lines.join("\n")}`);
      }

      default:
        throw new Error(`Unknown tool: ${name}`);
    }
  });
}
  • src/tools.ts:401-403 (helper)
    Helper function 'addrHex' used by the handler to format the breakpoint address as a hex string like '0xXXXXXXXX'.
    function addrHex(n: number): string {
  return `0x${n.toString(16).toUpperCase().padStart(8, "0")}`;
}
  • src/ppsspp.ts:235-272 (helper)
    The 'call' method on PpssppClient that sends a JSON-RPC message over WebSocket and awaits a ticketed response. The breakpoint handler uses this to call 'cpu.breakpoint.remove'.
      async call<T extends Record<string, unknown> = Record<string, unknown>>(
    event: string,
    params: Record<string, unknown> = {},
  ): Promise<T> {
    // Auto-(re)connect on demand. PPSSPP can be launched, closed, relaunched
    // at any point during the MCP server's lifetime; ensureConnected() will
    // bring the socket back up (or throw a clear error if PPSSPP isn't
    // reachable). Without this, a single failed connect at MCP boot would
    // leave every subsequent tool call broken until MCP-client restart.
    await this.ensureConnected();
    return new Promise<T>((resolve, reject) => {
      const ticket = `t${this.nextTicket++}`;
      const pending: PendingCmd = {
        ticket,
        resolve: (r) => resolve(r as T),
        reject,
      };

      const timer = setTimeout(() => {
        this.inflight.delete(ticket);
        reject(new Error(
          `PPSSPP call "${event}" timed out (${this.timeoutMs}ms) — ` +
          `is PPSSPP running with "Allow remote debugger" enabled?`,
        ));
      }, this.timeoutMs);
      const origResolve = pending.resolve, origReject = pending.reject;
      pending.resolve = (r) => { clearTimeout(timer); origResolve(r); };
      pending.reject  = (e) => { clearTimeout(timer); origReject(e); };

      this.inflight.set(ticket, pending);
      const msg = JSON.stringify({ event, ticket, ...params });
      if (process.env.MCP_PPSSPP_DEBUG) {
        process.stderr.write(`[trace] TX: ${msg}\n`);
      }
      this.ws!.send(msg);
    });
  }
}

Tool Definition Quality

A4.3/5.0
Behavior4/5

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

No annotations provided, so description carries full burden. It discloses idempotent behavior for non-existent breakpoints and states it modifies the breakpoint table, which is beyond what annotations would provide.

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?

Three concise sentences structured with 'PURPOSE', 'USAGE', 'BEHAVIOR', 'RETURNS'. No unnecessary words, front-loaded.

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?

Simple tool with one parameter and no output schema. Description covers purpose, usage, behavior, and return value completely. No gaps.

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?

Single parameter 'address' with 100% schema coverage. Schema description already explains it as 'PSP execution address'. Description adds no additional semantic value 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?

Description clearly states the verb 'Remove' and resource 'CPU execution breakpoint'. It distinguishes from siblings like ppsspp_breakpoint_add and ppsspp_breakpoint_list.

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

Usage Guidelines4/5

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

Explicitly says 'Clean up breakpoints when done debugging' and suggests using ppsspp_breakpoint_list to remove all. Provides clear context for when to use.

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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