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IDA-MCP

IDA-MCP

by Captain-AI-Hub
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Python
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Read Scalar

read_scalar

Read scalar integers with an explicit byte width from one or more addresses, optionally as signed, to inspect values during reverse engineering.

Instructions

Read scalar integer(s) with explicit width.

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": {
      "addr": "<addr>"
    },
    "name": "read_scalar"
  }
}

Input Schema

NameRequiredDescriptionDefault
addrYesAddress(es) - single or comma-separated
widthNoScalar width in bytes: 1, 2, 4, or 8
signedNoWhether to decode as signed integer
timeoutNoTimeout in seconds
instance_idNoREQUIRED whenever more than one database is open (from open_database's result or list_databases()); optional only while exactly one instance is live.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.0.1
    • changedInput schema / properties / instance_id / description
      Previous value: -"Instance id override"New value: +"REQUIRED whenever more than one database is open (from open_database's result or list_databases()); optional only while exactly one instance is live."
  2. First observedv0.9.7

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 disclosure burden. It does not state that this is a read-only operation, what happens on unmapped/invalid addresses, how multiple comma-separated addresses are returned, or whether reads require an open database or debugger session.

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 short sentence with the key qualifier ('explicit width') front-loaded and no filler. Brevity is appropriate, though the terseness borders on under-specification rather than pure economy.

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 5-parameter read tool with no annotations and no output schema, the description is thin. It omits the return shape—especially important because addr accepts comma-separated multiple addresses—and does not clarify the database/debugger context required to invoke it correctly.

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 already documents every parameter including width values, signedness, timeout, and the instance_id requirement. The description only restates 'explicit width' and adds nothing about multi-address addressing behavior.

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?

States a specific verb and resource (read scalar integers) plus the distinguishing trait of explicit width. It is clear enough to separate from get_bytes, but it does not name or contrast with the nearest sibling (dbg_read_mem) that also reads memory.

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 guidance on when to choose this over get_bytes, dbg_read_mem, or linear_disasm. Nothing says whether this reads from an IDB-backed view or a live debug target, which is the key selection question among siblings.

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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