USBTMC MCP Server

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usbtmc_list_devices

Read-onlyIdempotent

Identify all USBTMC test instruments connected via USB, returning their manufacturer, product, and serial number for device selection.

Instructions

List all available USBTMC devices connected via USB.

This is typically the first step in the workflow:

usbtmc_list_devices() - Discover available devices
usbtmc_connect() - Connect to a device and get device_id
Use device_id for operations (send/query/etc.)
usbtmc_disconnect() - Close connection when done

Returns: dict: Result containing: - count (int): Number of devices found - devices (list[dict]): List of device info dictionaries, each containing: - manufacturer (str): Device manufacturer name - product (str): Device product/model name - serial_number (str): Unique device serial number

Example: >>> result = usbtmc_list_devices() >>> result { "count": 1, "devices": [ { "manufacturer": "Keysight Technologies", "product": "DSO-X 3024A", "serial_number": "MY12345678" } ] }

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 9, 2026

TDQS

A3.9/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds the return format and example but no additional behavioral traits such as edge cases or limitations. Given the annotation coverage, the description provides minimal extra behavioral information.

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 a clear first sentence, workflow list, and example. It is slightly verbose for a parameterless tool, but the extra information about return format and workflow is useful. It earns its length.

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?

The tool is simple (no parameters), and the description fully covers purpose, when to use, return structure, and an example. Despite the existence of an output schema, the description itself provides sufficient detail for an agent to invoke correctly.

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

Parameters4/5

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

The tool has zero parameters, so the description need not explain parameter semantics; the baseline of 4 applies. The schema confirms no parameters, and the description correctly focuses on return values.

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?

The description clearly states the tool's function: 'List all available USBTMC devices connected via USB.' It also provides a workflow showing it's the discovery step. However, it doesn't explicitly differentiate from the sibling tool usbtmc_list_connected_devices, which may have overlapping purpose.

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

Usage Guidelines4/5

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

The description includes a numbered workflow: 'usbtmc_list_devices() - Discover available devices' and labels it as 'typically the first step.' This gives clear context for when to use it, but it does not mention when not to use it or alternatives.

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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