Parse a POSIX/Vixie cron expression and return the next N fire times plus an English description. Timezone-aware (IANA). Best-effort accuracy. Billed at 1 EUR cent per successful call; non-2xx responses are refunded.
| Name | Required | Description | Default |
|---|---|---|---|
| n | No | Number of upcoming fire times to return. | |
| tz | No | IANA timezone (e.g. 'Europe/Lisbon'). Defaults to UTC. | |
| cron | Yes | POSIX/Vixie cron expression (5 fields, e.g. '*/15 * * * *'). |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Discloses timezone awareness, best-effort accuracy, billing cost, and refund policy. With no annotations, this provides essential behavioral context. Could mention error handling for invalid cron expressions.
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?
Three sentences cover purpose, features, and billing without redundancy. Each sentence adds unique value, making it highly efficient.
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 should detail return format. It mentions 'next N fire times plus an English description' but lacks specifics on structure or fields, leaving some ambiguity.
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 100%, so the schema already describes each parameter. The description adds context for 'tz' (timezone-aware) but does not add new meaning beyond schema for 'cron' or 'n'.
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 clearly states the tool parses a cron expression and returns next fire times with an English description. 'Parse' and 'return' specify action and output, leaving no ambiguity.
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?
No guidance on when to use this tool versus alternatives (none listed). Does not mention prerequisites or context where this tool is appropriate or should be avoided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Only one tool exists, so there is no ambiguity or risk of misselection. The tool's purpose is clear and distinct.
Single tool uses a consistent verb_noun pattern (explain_cron), which is clear and follows common conventions.
With only one tool, the server feels thin for a typical MCP server. While the tool itself is focused, a single tool is borderline for general utility.
The tool fully covers the core functionality of explaining a cron expression with fire times and descriptions. However, there are no auxiliary tools for validation or alternative formats, leaving minor gaps.