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Universal Game Modder

Universal Game Modder

by doritoman90000
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jar_edit_class_constants

Edit numeric constants in Java .class bytecode to alter compiled game behavior, replacing old values with new ones without source code.

Instructions

Edit numeric constants in .class file bytecode.

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": {
      "session_id": "<session_id>",
      "class_path": "<class_path>",
      "replacements": "<replacements>"
    },
    "name": "jar_edit_class_constants"
  }
}

Input Schema

NameRequiredDescriptionDefault
class_pathYesPath to .class file
occurrenceNoWhich occurrence to replace (0-indexed)
session_idYesSession ID
value_typeNoValue type hint
replacementsYesMap of old_value -> new_value

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.4

TDQS

C2.9/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full behavioral burden. 'Edit' implies mutation, but it doesn't say whether the change is in-place on disk, scoped to an open session, reversible, or what happens if no occurrence matches - all critical for a bytecode-mutating tool.

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?

A single front-loaded sentence with no filler, clearly stating verb and target. It is arguably undersized for a 5-parameter mutation tool, but nothing in it is wasted.

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?

For a mutation tool with no annotations, no output schema, and a nested `replacements` object, the description omits too much: session requirements (session_id is required), failure behavior, and how the bytecode rewrite is applied. The agent cannot call this confidently.

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 the schema itself documents all five parameters, establishing a baseline of 3. The description adds nothing about the semantics of `replacements` (old_value -> new_value mapping), `occurrence` indexing behavior, or `value_type` hints.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb and resource: 'Edit numeric constants in .class file bytecode.' This is distinguishable in principle from siblings like jar_edit_constant_pool and jar_hex_edit, but the description never explicitly contrasts itself with them, leaving the agent to infer which editing tool to pick.

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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives such as jar_edit_constant_pool or jar_hex_edit. The agent gets no routing help among several overlapping jar-editing tools.

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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