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usb-rea

usb-rea

by emirmrkaljevic
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
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capture_start

Start capturing USB traffic to a pcapng file for protocol reverse engineering. Requires elevated privileges on Linux; pair with capture_stop.

Instructions

Start a USB traffic capture into out (usbmon on Linux, USBPcap on Windows).

Side effects: launches a background capture process that keeps writing until capture_stop. Needs elevated privileges on Linux (usbmon; typically root or a usbmon group). Does not touch the device itself. Pair every start with capture_stop; do not start a second capture while one is running. Prefer this over analysis tools when you still need live traffic.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "capture_start"
  }
}

Input Schema

NameRequiredDescriptionDefault
busNousbmon bus number N for /dev/usbmonN; ignored on Windows/USBPcap. Default 0
outNoOutput pcapng path (overwritten if it already exists)capture.pcapng

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv0.2.1
    • addedInput schema / properties / bus / description
      Added value: +"usbmon bus number N for /dev/usbmonN; ignored on Windows/USBPcap. Default 0"
    • addedInput schema / properties / out / description
      Added value: +"Output pcapng path (overwritten if it already exists)"
  2. First observedv0.2.0

TDQS

A4.5/5.0
Behavior4/5

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

No annotations exist, so the description carries the full burden, and it does so well: it discloses the side effect of launching a persistent background process, the elevation requirement on Linux, and that it does not touch the device. It stops short of covering output-file overwrite semantics or failure/cleanup behavior, keeping it from a 5.

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

Conciseness5/5

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

Four short, front-loaded sentences with zero filler; the primary purpose and output target come first, followed by side effects and usage rules. Every sentence earns its place.

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?

An output schema exists, so return values need not be described. For a side-effecting, no-annotation tool with elevated-privilege requirements, the description covers purpose, side effects, permissions, lifecycle, and routing — the agent has everything needed 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 both parameters are already documented in the schema. The description references `out` but adds no semantics (e.g., overwrite behavior) beyond what the schema states, so the baseline 3 applies.

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?

States a specific verb (start) and resource (USB traffic capture) and names the output target, with platform nuance (usbmon on Linux, USBPcap on Windows). An agent can immediately distinguish this from capture_stop, which it explicitly pairs with.

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?

Explicit when-to-use guidance ('prefer this over analysis tools when you still need live traffic'), a hard when-not constraint ('do not start a second capture while one is running'), and a lifecycle rule ('pair every start with capture_stop'). Nothing is left to inference.

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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