Explain a five-field cron expression in plain English, list the next runs in UTC, and warn about the cases Cloudflare Workers, GitHub Actions and crontab handle differently (nicknames, six fields, day-of-month plus day-of-week, sub-5-minute intervals, day 31).
| Name | Required | Description | Default |
|---|---|---|---|
| from | No | ISO date to compute next runs from, default now | |
| count | No | How many next runs to list, 1 to 20, default 5 | |
| expression | Yes | e.g. 0 */6 * * 1-5 |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare a safe read-only, closed-world operation, so the safety profile is covered. The description adds real behavioral context beyond them: results are computed in UTC and the tool flags platform-specific cron divergences (nicknames, six fields, day-31), which an agent could not infer from the schema.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single front-loaded sentence that names the core action first, then the two secondary outputs. Every clause carries information; nothing is boilerplate or redundant.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description must describe returns, and it does: plain-English explanation, next-run list in UTC, and dialect warnings. For a focused read-only utility this is fully sufficient for correct invocation.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so 'expression', 'from' and 'count' including their defaults and ranges are already documented in the schema. The description adds nothing about parameter syntax or the accepted expression format beyond what is structured, so the baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb (explain) and resource (five-field cron expression) and enumerates the three outputs: plain-English explanation, next runs in UTC, and dialect warnings. It is unmistakably distinct from every sibling tool, none of which touch cron.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
It gives clear context for what the tool covers (five-field expressions, UTC next runs, dialect pitfalls), which tells an agent when this is the right tool. It stops short of explicit when-not-to-use guidance, but no sibling overlaps, so the omission is minor.
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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