Why no run?

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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds real value beyond them: it discloses the return content (previous/next scheduled runs), dialect-specific AND-rule and DST notes, and the timezone interpretation rule for offset-less timestamps.

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?

Front-loaded with the core purpose and a clarifying example, followed by the timestamp/timezone rule and the conditional fallback. Dense but every sentence carries signal; the nested parenthetical example is slightly bulky but earns its place as disambiguation.

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?

An output schema exists, so return values needn't be detailed, yet the description still sketches the answer's shape (previous/next runs, rule notes). Combined with the timezone and DST disclosures, it is nearly complete; the only shortfall is the uninterpreted `name` parameter.

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 carry full burden. It explains `at` well (ISO 8601, offset-less values use the job's time zone), but leaves `name` entirely uninterpreted—an agent must infer it identifies the job. Partial compensation warrants a middling score.

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?

Specific verb+resource: 'Explain field-by-field why a job's schedule did or did not select a timestamp', with a concrete worked example ('day-of-week Tuesday is not in Monday and Friday'). An agent can clearly tell this is a diagnostic/explanatory tool distinct from siblings like cron_validate_schedule or cron_explain_schedule.

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?

Explicitly states the fallback: 'If the schedule does match, the answer refers to execution history (cron_list_runs) instead', routing the agent to the right sibling when this tool is not applicable. It does not, however, distinguish itself from cron_explain_schedule or cron_validate_schedule, which is a gap given the dense sibling set.

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