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

Annotations already declare readOnlyHint=true, but the description adds valuable behavior: determinism, support for 5/6 field expressions, timezone-awareness, and specific mentions of DST and DOM/DOW logic. This exceeds the minimal and provides helpful context beyond annotations.

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 two sentences, front-loaded with the primary purpose and then a rationale. Every clause adds value, with no redundancy or fluff.

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?

Given the tool's moderate complexity, the description covers the main use cases (validation, scheduling, timezone handling) and even highlights edge cases (DST, OR-logic). With no output schema, it clearly states that it computes fire times, providing sufficient context.

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 baseline is 3. The description adds semantics like '5 or 6 field, seconds optional' and 'timezone-aware', which supplement the schema's parameter definitions and help interpret the 'expression' and 'timezone' parameters.

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: 'parses a cron expression... and computes the next N actual fire times'. It distinguishes itself from siblings by its specific focus on cron validation and scheduling, and no sibling offers similar functionality.

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 explicit guidance: 'Use this instead of guessing' and explains common pitfalls (DOM/DOW OR-logic, DST transitions). While no alternative tool is named, the guidance is clear and context-specific.

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