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laszlopere

mcp-gnu-units

list_prefixes

List every SI and binary prefix with its exact multiplier to find correct spellings for unit conversions.

Instructions

List every SI and binary prefix in the GNU units database with its multiplier (TODO §13).

Enumerates all defined prefixes — the SI decimal ladder (quettaquecto and their symbols Qq) plus the binary/IEC prefixes (kibi/Ki, mebi/Mi, …) — sorted by descending magnitude. Useful for discovering the exact prefix spelling to use in a convert or convert_to_si expression, or for seeing a prefix's exact numeric value.

Returns: count (number of prefixes) and prefixes, a list of objects each with name (the prefix, without its trailing hyphen) and multiplier (its value as a string, exact where the value is an exact integer, e.g. kibi -> "1024", mega -> "1000000"). Example: list_prefixes() -> {"count":125,"prefixes":[{"name":"quetta","multiplier":"1000000000000000000000000000000"}, ...,{"name":"kibi","multiplier":"1024"}, ...]}

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Behavior4/5

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

No annotations provided, but the description discloses return structure (count and list of objects with name and multiplier), sorting order, exactness of values, and gives an example. It mentions a TODO but does not indicate any destructive behavior or rate limits.

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?

The description is well-structured: a concise summary line, followed by explanation of contents, usage, return format, and example. Every sentence adds value and it is front-loaded.

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?

Given no parameters, no output schema, and low complexity, the description is complete. It covers purpose, usage, return format, and an example. The TODO note is minor and does not detract.

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 no parameters, so the input schema fully covers the meaning. The description adds context about the output structure and purpose, but no parameter explanation is needed.

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 it lists all SI and binary prefixes from the GNU units database, sorted by descending magnitude. It distinguishes itself from sibling tools by specifying its use for discovering prefix spellings and values.

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 explicitly says it is useful for discovering prefix spellings for convert or convert_to_si expressions, and for seeing exact numeric values. It implies usage context but does not explicitly state when not to use it.

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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