Underground Cultural District MCP Server

build-cron

Parse any cron expression and get a clear, plain-English explanation of each field, including minute, hour, day, month, and weekday.

Instructions

Parse a cron expression and explain what each field means in plain English.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "expression": "<expression>"
    },
    "name": "build-cron"
  }
}

Input Schema

Name	Required	Description	Default
`expression`	Yes	Cron expression, e.g. '0 9 * * 1'

Schema Changelog

Changes observed during successful MCP inspections.

First observedv4.1.0Apr 17, 2026

TDQS

A3.5/5.0

Behavior2/5

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

With no annotations provided, the description must fully disclose behavior. It only states the basic parse-and-explain functionality, omitting details about error handling (e.g., invalid expressions), input validation, or the structure of the explanation, leaving significant gaps for the agent.

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 a single, front-loaded sentence that directly conveys the tool's purpose without any extraneous words. It is highly efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple tool with one parameter and no output schema, the description covers the core intent but lacks details on the return format or error scenarios. It is adequate but not complete.

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 coverage is 100% with a clear description of the 'expression' parameter including an example. The tool description does not add additional meaning beyond what the schema already provides, which meets the baseline for high coverage.

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 the action ('Parse a cron expression') and the result ('explain what each field means in plain English'). It is specific to cron expressions and distinct from sibling tools that perform other conversions or analyses.

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?

The description implies usage: when a user needs to understand a cron expression. However, it does not explicitly state when not to use it or suggest alternatives, leaving the decision to the agent's inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.