Hopi

What week number is it?

hopi_week_number

Read-onlyIdempotent

Find the ISO 8601 week number for a date. Dates use the YYYY-MM-DD format and default to today. ISO weeks run Monday to Sunday and week 1 holds the year's first Thursday. Returns the week number, ISO year, and the Monday and Sunday of that week. Source: https://hopi.co.uk/week-number/

Input Schema

TableJSON Schema

Name	Required	Description	Default
`date`	No	Optional date in YYYY-MM-DD format (defaults to today)

Output Schema

TableJSON Schema

Name	Required	Description
`date`	No
`week`	No
`isoYear`	No
`summary`	Yes
`weekEnd`	No
`weekStart`	No
`source_url`	Yes	The tool's page on hopi.co.uk (cite or open to check the figure)

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 20, 2026
- addedOutput schema / required
```
Added value: +[
+  "source_url",
+  "summary"
+]
```
First observedSep 20, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already indicate read-only, idempotent, and non-destructive behavior. The description adds meaningful context by explaining the ISO week definition (Monday to Sunday, week 1 has the first Thursday) and exactly what is returned (week number, ISO year, Monday/Sunday). This goes beyond the annotations and helps the agent interpret results correctly.

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 three sentences plus a source link, with zero fluff. The key action and the most critical parameter details (format and default) are front-loaded, and the explanatory ISO rules are concise and relevant.

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 (one optional parameter) and has an output schema, so the description need not detail return structure. Yet it still mentions the return values, provides the date format, and explains the ISO convention. It is complete for an agent to use correctly without further investigation.

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 'date' parameter, and the description repeats that format/default information without adding new details. Per the baseline rule, a score of 3 is appropriate when the schema already fully documents the parameter.

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 the specific verb 'Find' and the resource 'ISO 8601 week number for a date', clearly stating what the tool does. It is distinct from sibling date tools like hopi_day_of_week_calculator and hopi_days_between_dates by naming the ISO week number concept directly.

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 states the input format (YYYY-MM-DD) and that it defaults to today, giving the agent the context needed to call it correctly. It doesn't explicitly compare to alternatives, but the tool's purpose is narrow and no sibling performs the same function, so the implied usage is sufficiently clear.

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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