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ppsspp_write8

Write a single unsigned byte (0-255) to a PSP physical memory address. Use for cheat codes, debug pokes, and game-state mutations.

Instructions

PURPOSE: Write an unsigned byte (0-255) to PSP memory at the given physical address. USAGE: Use for single-byte cheats, debug pokes, game-state mutations. For 16/32-bit use ppsspp_write16/write32; for spans use ppsspp_write_range. BEHAVIOR: DESTRUCTIVE: overwrites whatever was at address with no undo. Direct memory write — no hardware mediation. Returns an error if the address is outside valid memory or value > 255. RETURNS: Single line 'Wrote VAL → ADDR_HEX'.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
addressYesPSP physical address. PSP memory layout: user RAM starts at 0x08800000 (or 0x08000000 — varies by firmware allocation), kernel RAM at 0x08000000-0x087FFFFF, VRAM at 0x04000000-0x041FFFFF, scratchpad at 0x00010000-0x00013FFF, hardware regs at 0xBC000000+. Most game state lives in user RAM. Note PPSSPP may also accept 0x88xxxxxx kernel-mode mirrors of the same physical memory.
valueYesByte value (0-255).

Implementation Reference

  • src/tools.ts:146-162 (registration)
    The 'ppsspp_write8' tool is registered in the TOOLS array with its name, description, and inputSchema (address + value 0-255).
    {
      name: "ppsspp_write8",
      description:
        "PURPOSE: Write an unsigned byte (0-255) to PSP memory at the given physical address. " +
        "USAGE: Use for single-byte cheats, debug pokes, game-state mutations. For 16/32-bit use ppsspp_write16/write32; for spans use ppsspp_write_range. " +
        "BEHAVIOR: DESTRUCTIVE: overwrites whatever was at `address` with no undo. Direct memory write — no hardware mediation. Returns an error if the address is outside valid memory or value > 255. " +
        "RETURNS: Single line 'Wrote VAL → ADDR_HEX'.",
      inputSchema: {
        type: "object",
        required: ["address", "value"],
        properties: {
          address: { type: "integer", minimum: 0, description: ADDRESS_PARAM_DESC },
          value:   { type: "integer", minimum: 0, maximum: 255, description: "Byte value (0-255)." },
        },
        additionalProperties: false,
      },
    },
  • The handler for 'ppsspp_write8' calls pp.call('memory.write_u8', ...) to write a byte to PSP memory, then returns a confirmation string.
    case "ppsspp_write8": {
      await pp.call("memory.write_u8", { address: a(), value: p.value });
      return ok(`Wrote ${fmtHex(p.value)} → ${addrHex(a())}`);
    }
Behavior5/5

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

The description explicitly declares the tool as DESTRUCTIVE with no undo, mentions direct memory write without hardware mediation, and states error conditions (address out of valid memory or value > 255). No annotations are provided, so the description fully covers behavioral traits.

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

Conciseness4/5

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

The description is compact with clear sections (PURPOSE, USAGE, BEHAVIOR, RETURNS) and front-loads the purpose. Every sentence is useful, though the return format could be slightly more concise. Overall efficient.

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

Completeness4/5

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

Given the tool's simplicity (2 required parameters, no output schema), the description covers purpose, usage, behavior, and return format. It includes memory layout hints in the schema. Minor missing details about writable memory ranges, but adequate for a low-complexity tool.

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 baseline is 3. The description reiterates the parameter constraints (0-255, physical address) but does not add significant new meaning beyond the schema's own parameter descriptions. It provides context in the BEHAVIOR section but no parameter-specific enhancements.

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 action: writing an unsigned byte (0-255) to PSP memory at a physical address. It specifies the resource and differentiates from sibling tools by explicitly mentioning ppsspp_write16/write32 for 16/32-bit and ppsspp_write_range for spans.

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 USAGE section explicitly states when to use this tool (single-byte cheats, debug pokes, game-state mutations) and when not to, naming alternative tools for 16/32-bit and range writes. This provides clear guidance for selection.

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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