Cron -> next N runs + description (paid $0.001)

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

With no annotations, the description carries the full burden of disclosing non-obvious behavior. It explicitly reveals the paid nature ($0.001), the x402 challenge when payment is omitted, and how to settle via x_payment. This goes beyond the schema and covers critical behavioral context.

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?

The description is compact and well-structured. It front-loads the cost warning, then explains the core functionality, summarizes arguments, and closes with the payment challenge behavior. Every sentence adds a distinct piece of information with no filler.

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?

The description covers key contextual aspects: accepted cron format, default values, payment requirement, and the high-level result (run times plus description). While the exact return structure isn't detailed, the tool is relatively simple and the absence of an output schema is partially compensated by this clear summary.

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?

The schema description coverage is 100%, so the input schema already documents all parameters. The description repeats argument names and defaults (timezone, count, from) without adding new semantic meaning or clarifications beyond what the schema provides.

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's function: 'Parse a 5- or 6-field cron expression and return the next N run times plus a plain-English description.' This uses a specific verb and identifies both the input and output, distinguishing it from sibling tools like rrule.

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?

The description provides a clear context of what the tool does, so the agent can infer when to use it, but it does not explicitly mention alternative tools (e.g., rrule) or provide 'when not to use' guidance. Usage is implied rather than stated.

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