PCSX2 MCP

by snowyegret23

Overview Schema Source Related Servers Discussions Admin

Python

Local

write_register

Overwrite any CPU register by name or numeric index in PCSX2 to modify emulation state.

Instructions

Overwrite one register by name or numeric index.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "register": "<register>",
      "value": "<value>"
    },
    "name": "write_register"
  }
}

Input Schema

Name	Required	Default
`value`	Yes
`target`	No	ee
`register`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jul 27, 2026

TDQS

C2.9/5.0

Behavior2/5

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

The description states 'overwrite', indicating a destructive write operation, but lacks details on side effects (e.g., overwriting read-only registers), permissions needed, reversibility, or consequences for other state. With no annotations, this is insufficient for a mutation tool.

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

Conciseness3/5

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

The description is a single concise sentence, but it is too brief. It lacks structure for multiple parameters and could benefit from breaking down the information in a way that aids understanding.

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

Completeness2/5

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

Given the tool has three parameters, no annotations, and no output schema, the description is incomplete. It does not explain the 'target' or 'value' parameters, nor does it describe return values or behavior for edge cases.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds meaning for the 'register' parameter (name or numeric index), but the 'value' and 'target' parameters are not explained. Schema description coverage is 0%, so the description should compensate, but it only partially addresses one of three parameters.

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 ('overwrite'), the resource ('register'), and the method of identification ('by name or numeric index'). It distinguishes this tool from siblings like 'get_registers' and 'write_debug_register', establishing a specific purpose.

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

Usage Guidelines2/5

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

No guidance is provided on when to use this tool versus alternatives like 'write_debug_register' or 'get_registers'. There is no mention of prerequisites, limitations, or scenarios where using this tool is appropriate or inappropriate.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.