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

With no annotations, the description carries the full burden and does disclose non-obvious traits: the paid nature (1000 atomic USDC) and that payment authorization is required before execution. These are important gating behaviors absent from the schema. It stops short of describing failure behavior or how the returned times are formatted.

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, front-loaded with the purpose before scope exclusions and cost. Every sentence carries distinct information (capability, limitations, payment) 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?

For a stateless calculator with no output schema and no annotations, the description covers the return shape in general terms, cost, and auth. It is adequate overall but omits the after_utc format details and any error/edge-case behavior an agent would need for reliable 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 0%, so the description must compensate for all three required parameters. 'Up to five next UTC times' maps to count and 'numeric five-field cron' partially constrains expression, but after_utc receives no explanation at all (format, meaning, or relationship to the results), leaving a required parameter undocumented in both schema and description.

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 ('Calculate') and resource ('next UTC times') plus the exact input constraint ('numeric five-field cron with wildcard day-of-month or weekday'). The scope is unambiguous, though the unrelated sibling set means there is no analogous tool to differentiate against.

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 timezone, named fields, or delivery' communicates meaningful exclusions that tell the agent when this tool is unsuitable, which is real guidance. However, no alternative tool or positive when-to-use condition is named, leaving selection judgment implied rather than explicit.

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