Explain a standard 5-field cron expression (minute hour day-of-month month day-of-week) in plain English and list its next run times in a given time zone, handling daylight saving time.
| Name | Required | Description | Default |
|---|---|---|---|
| count | No | ||
| timeZone | No | IANA time zone, e.g. Asia/Kolkata or America/New_York | UTC |
| expression | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is low. The description goes further by disclosing the output form (plain English plus next run times) and the non-obvious DST-handling behavior, which is genuinely useful. It stops short of saying what happens on a malformed expression or how the 'count' cap behaves.
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?
One dense sentence with no filler; the core action is front-loaded and the qualifiers (field layout, time zone, DST) follow. It is efficient, though the parenthetical field enumeration makes it slightly heavy for a single sentence.
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 correctly carries the return-value burden, naming both the explanation and the next-run list, and covers the DST subtlety. The remaining gap is the undocumented 'count' parameter and error behavior for invalid expressions.
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 coverage is only 33% (only timeZone is documented in the schema). The description partially compensates by explaining the expression format (5 fields, with their meanings) and the time-zone input, but 'count' is never mentioned in either place, leaving its meaning to be inferred from the name and default of 5.
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?
States a specific verb ('explain') and resource ('standard 5-field cron expression'), plus the two outputs (plain-English explanation, next run times) and the time-zone/DST scope. It is unambiguous what the tool does, though it does not differentiate itself from any sibling since none of the other listed tools 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?
Usage is implied rather than stated: an agent can infer this is the tool for cron expressions, but there is no explicit 'use this when...' framing, no when-not guidance, and no named alternative for related tasks such as timestamp conversion (usesignal_convert_timestamp).
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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