Hopi

Leap year checker

hopi_leap_year_checker

Read-onlyIdempotent

Check whether a year is a leap year, applying the divisible-by-4, century, and divisible-by-400 rules. Returns the verdict, the divisibility tests, and the next and previous leap years. Source: https://hopi.co.uk/leap-year-checker/

Input Schema

TableJSON Schema

Name	Required	Description	Default
`year`	Yes	The year to check (1 to 9999)

Output Schema

TableJSON Schema

Name	Required	Description
`year`	Yes
`summary`	Yes
`isLeapYear`	Yes
`source_url`	Yes	The tool's page on hopi.co.uk (cite or open to check the figure)
`divisibleBy4`	Yes
`nextLeapYear`	Yes
`divisibleBy100`	Yes
`divisibleBy400`	Yes
`previousLeapYear`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 20, 2026

addedOutput schema / required

Added value: +[
+  "divisibleBy100",
+  "divisibleBy4",
+  "divisibleBy400",
+  "isLeapYear",
+  "nextLeapYear",
+  "previousLeapYear",
+  "source_url",
+  "summary",
+  "year"
+]

First observedSep 20, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds value by disclosing the applied rules and what is returned (verdict, divisibility tests, next/previous leap years), providing behavioral context beyond the annotations.

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?

Two sentences that front-load the core purpose and then list the return content, followed by a source URL. It is compact, every sentence carries meaningful information, and no redundant details dilute the message.

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?

For a simple one-parameter tool with an output schema, the description fully covers what the operation does, the rule set applied, and what the result includes. An agent can correctly select and invoke the tool without needing additional context.

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% for the single `year` parameter, so the schema already documents it fully. The description mentions 'a year' but adds no extra parameter-level detail; baseline 3 is appropriate.

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 opens with 'Check whether a year is a leap year', giving a specific verb and resource, and elaborates with the exact rules (divisible-by-4, century, divisible-by-400). This unambiguously identifies the tool's function among the extensive list of sibling calculators.

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

Usage Guidelines3/5

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

No explicit when-to-use or alternatives are mentioned. Usage is implied by the self-evident purpose ('Check whether a year is a leap year'), but there is no guidance on when not to use it or which sibling tools might be relevant.

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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