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

Annotations already declare readOnlyHint and openWorldHint, and the description adds meaningful behavior beyond that: returns UTC ISO 8601 plus local wall-clock rendering, refuses Quartz-only syntax rather than guessing, and produces no prose. This is rich, accurate behavioral context with no contradiction.

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 front-loaded and well-organized with a clear purpose sentence, but it is longer than necessary. The "WHY DELEGATE THIS" section repeats some of the earlier warning about manual calculation, and the "Owned by Cron Translator... callable directly" sentence adds little for an agent selecting the tool.

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 tool with no output schema, the description adequately explains the return format, timezone behavior, and syntax limitations, while the schema covers parameter defaults. It is slightly incomplete on error behavior for invalid expressions, but the core information needed to call and interpret the tool is present.

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 baseline is 3 even without extra parameter detail. The description does add some value by clarifying timezone semantics (UTC instant plus local rendering) and expression limitations, but it does not add much about count or expression beyond what the schema already states.

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 opens with a specific verb and resource: "Lists the next run times for a cron expression in a specific timezone." It also clarifies that the output is "with no prose," which distinguishes it from explanation-style sibling tools like cron_explain.

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?

It explicitly says to use the tool when the only question is "when does this next fire" and gives concrete scenarios: job deadlines and upcoming schedules. It also warns against manual computation. However, it does not explicitly name sibling alternatives or state when not to use it, only implying the boundary through the question phrasing.

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