Hopi

Litres to pints converter

hopi_litres_to_pints

Read-onlyIdempotent

Convert between litres and pints. Direction 'litres-to-pints' takes litres and returns UK pints, US pints and millilitres. Direction 'pints-to-litres' takes UK pints and returns litres. Source: https://hopi.co.uk/litres-to-pints/

Input Schema

TableJSON Schema

Name	Required	Description	Default
`value`	Yes	The value to convert (litres or UK pints depending on direction)
`direction`	Yes	Which way to convert

Output Schema

TableJSON Schema

Name	Required	Description
`litres`	Yes
`summary`	Yes
`ukPints`	Yes
`usPints`	No
`direction`	Yes
`source_url`	Yes	The tool's page on hopi.co.uk (cite or open to check the figure)
`millilitres`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 20, 2026

addedOutput schema / required

Added value: +[
+  "direction",
+  "litres",
+  "source_url",
+  "summary",
+  "ukPints"
+]

First observedSep 20, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare the tool read-only and idempotent. The description adds valuable behavioral detail: litres-to-pints returns UK pints, US pints, and millilitres, while pints-to-litres only returns litres, revealing an important asymmetry in the tool's output that the schema alone does not show.

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 compact and front-loaded: the main purpose is stated in the first sentence, followed by concise direction-specific behavior, and a source link. There is no filler or redundant restatement of the schema.

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 has only two parameters and an output schema, and the description covers both directions, the expected input unit, and the output units. Nothing needed for correct invocation is missing, especially given the annotations already communicate safety.

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 schema already covers 100% of parameters, and the description goes further by explaining how each direction affects the meaning of `value` and what output units to expect. This adds context beyond the schema's generic descriptions.

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 starts with a clear verb and resource: 'Convert between litres and pints.' It then specifies both supported directions, making the tool's exact purpose unambiguous and differentiating it from generic unit converters and other hopi converter tools.

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 gives clear context for when to use the tool: any conversion between litres and UK/US pints. It does not explicitly name alternatives like hopi_volume_converter, but the precise scope and direction-based behavior make the intended usage evident.

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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