Hopi

Cron expression translator

hopi_cron_expression_parser

Read-onlyIdempotent

Translate a standard five-field cron expression (minute, hour, day-of-month, month, day-of-week) into plain English. Understands stars, steps, ranges, lists and month and day names, plus shortcuts like @daily and @hourly. Source: https://hopi.co.uk/cron-expression-parser/

Input Schema

TableJSON Schema

Name	Required	Description	Default
`expression`	Yes	A five-field cron expression, for example '/5 9-17 * MON-FRI', or a shortcut like @daily

Output Schema

TableJSON Schema

Name	Required	Description
`hour`	Yes
`month`	Yes
`minute`	Yes
`english`	Yes
`summary`	Yes
`dayOfWeek`	Yes
`dayOfMonth`	Yes
`expression`	Yes
`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: +[
+  "dayOfMonth",
+  "dayOfWeek",
+  "english",
+  "expression",
+  "hour",
+  "minute",
+  "month",
+  "source_url",
+  "summary"
+]

First observedSep 20, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already establish that the tool is read-only, idempotent, and non-destructive. The description adds useful behavioral context by specifying accepted input forms: stars, steps, ranges, lists, month/day names, and shortcuts such as @daily and @hourly. Error handling and edge-case behavior are not mentioned, but the output schema and safety annotations lower the burden.

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 compact and front-loaded with the core purpose in the first sentence. The second sentence adds useful supported-syntax detail, and the source URL is a minor extra that is not fully necessary but does not create significant noise.

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 one-parameter, read-only tool with a full output schema and strong annotations, the description is complete enough. It states the exact input format, the supported cron features, the shortcut extensions, and the transformation being performed, so an agent has sufficient information to invoke it correctly.

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%, so the schema already documents the single 'expression' parameter and provides an example. The description adds some breadth about accepted cron syntax, but most of that is either implied by or consistent with the schema, so it does not substantially exceed the schema baseline.

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 uses a specific verb and resource: 'Translate a standard five-field cron expression ... into plain English.' It also names the supported syntax features and shortcuts, making it easy for an agent to distinguish this tool from the many unrelated hopi utilities.

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 clearly implies when to use the tool: whenever a cron expression needs to be converted into readable English. It does not explicitly mention alternatives or exclusions, but no sibling tool appears to offer the same function, so the lack of explicit routing is a minor gap.

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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