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

Annotations already mark the tool as read-only and idempotent. The description confirms this by stating it never raises protocol errors and is read-only/idempotent, adding value by detailing error return format. However, the description could elaborate on side effects (even if none) or behavior under unexpected inputs beyond malformed ones.

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 well-structured: it starts with a one-line summary, provides a concrete example, then usage notes. Every sentence adds value, and it's appropriately sized for the tool's simplicity.

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 low complexity (one parameter, no enums, no nested objects, clear output schema), the description is complete. It covers input expectations, output format, error handling, and assumptions, with no gaps for the intended use case.

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 100%, so the schema already documents the parameter well. The description adds value by showing a usage example with expected output format, though it doesn't add much beyond clarifying input/output examples.

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 explains a 5-field cron expression in plain English and flags mistakes. It differentiates from siblings (e.g., diff_texts, json_validate) by being narrowly scoped to cron scheduling, not general text or code validation.

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 explicitly says when to use it (to read a schedule) and what it's not for (6-field or seconds-precision variants). It also notes it's safe to retry after correcting input, but doesn't explicitly contrast with non-sibling alternatives or edge cases like timezones.

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