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mcp-dolphin

dolphin_read64

Reads an unsigned 64-bit big-endian value from PowerPC memory at an 8-byte aligned address. Returns the result as a decimal string to preserve precision beyond 2^53.

Instructions

PURPOSE: Read an unsigned 64-bit big-endian value from PowerPC memory at the given absolute address. USAGE: For paired 32-bit slots, doubles, packed flags. PowerPC is 32-bit so true 64-bit fields are less common than on PS2 — usually game state is 32-bit. Use this when you actually have a 64-bit field, not as a convenience for two 32-bit reads. BEHAVIOR: No side effects — pure read. Address MUST be 8-byte aligned. The result is returned as a decimal STRING (not a JSON number) to preserve precision past 2^53. Returns an error on unmapped address, bridge disconnect, or FAIL.

GameCube + Wii main address space landmarks (PowerPC, big-endian): 0x80000000-0x817FFFFF MEM1 main RAM (24 MiB) — GameCube + Wii game code & data GameCube games stay entirely within MEM1. Wii games use MEM1 for code and frequently-accessed data. 0x80000020 OS_GLOBALS — game-info struct (disc ID, FST, etc.) 0x80000034 OS_ARENA_LO (start of free MEM1 heap) 0x80003100 OS_REPORT (developer-console mirror, varies by SDK) 0x90000000-0x93FFFFFF MEM2 (64 MiB) — Wii ONLY. Larger texture/asset data, IOS work areas. Reading MEM2 on a GameCube game returns garbage / FAIL. 0xCC000000-0xCC00FFFF Hollywood I/O (Wii) / Flipper I/O (GameCube) — DMA, GPU FIFO, AI, EXI registers. Reads are usually safe, writes can wedge the emulator. Avoid. 0xCD000000-0xCD007FFF Wii-only Hollywood registers.

Notes: • All multi-byte values are BIG-ENDIAN on the real hardware. Felk's memory.read_u*/write_u* helpers handle the byte swap for you — the value you see is the value the game sees as a u32. • Addresses are 32-bit; Felk truncates the high bits of any u64 address argument. • Pointers in MEM1 are often stored as 4-byte addresses with the high bit set (e.g. 0x81234567). Dereferencing them requires no masking — pass the raw value back into memory.read_*.

RETURNS: Single line 'ADDR_HEX: VAL_DEC (0xVAL_HEX)' — VAL_DEC is a decimal string that may exceed 2^53.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
addressYesAbsolute PowerPC virtual address (0x80000000-0x9FFFFFFF). Pass as a number; hex literals like 0x80001000 are fine. Reads 8 consecutive bytes starting here and interprets them as a big-endian value. MUST be 8-byte aligned (address % 8 === 0). PowerPC raises an alignment exception on misaligned access in hardware, but Dolphin's emulated bus is forgiving and silently returns the aligned-down word — i.e. you get the bytes from address & ~7, not what you asked for. For unaligned multi-byte reads use dolphin_read_range and assemble client-side. Useful ranges: 0x80000000-0x817FFFFF for MEM1 (GC + Wii), 0x90000000-0x93FFFFFF for MEM2 (Wii only).
Behavior5/5

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

No annotations are provided, so the description carries full responsibility. It declares 'No side effects — pure read.' It details alignment behavior (MUST be 8-byte aligned) and warns that misaligned accesses silently return aligned-down data. It explains the return format as a decimal string to preserve precision and lists error conditions (unmapped address, bridge disconnect, FAIL).

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 well-structured with sections (PURPOSE, USAGE, BEHAVIOR, memory landmarks, Notes, RETURNS) and front-loaded. While comprehensive, it is somewhat lengthy due to detailed memory map and general notes that could be condensed. Still, every section serves a purpose.

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 guidelines, behavioral details, parameter constraints, return format, and error conditions. The memory map and endianness notes provide essential context for correct usage.

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 coverage is 100%, so the baseline is 3. The input schema already thoroughly describes the address parameter (alignment, ranges, 8-byte read). The tool description adds some context (memory map, return format) but does not significantly enhance understanding of the parameter itself beyond what the schema 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: 'Read an unsigned 64-bit big-endian value from PowerPC memory at the given absolute address.' It specifically contrasts with smaller reads (e.g., 'usually game state is 32-bit') and advises using this only for actual 64-bit fields, effectively distinguishing it from sibling tools like dolphin_read32.

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 explicitly states when to use ('Use this when you actually have a 64-bit field') and when not to ('not as a convenience for two 32-bit reads'). It provides alignment requirements (8-byte aligned) and directs unaligned reads to dolphin_read_range. The memory map helps users choose valid addresses.

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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