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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real behavioral context beyond them: DST correctness, the day-of-month OR day-of-week rule and its reporting, precise rejection of invalid expressions, and a pricing/auth note ($0.01 USDC via x402 on Solana) plus an HTTPS endpoint. These are details the annotations do not convey.

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-loads the core function, then capabilities, then validation behavior, then pricing/alternate endpoint. Dense but every clause carries information; nothing is redundant.

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?

With no output schema, the description explains the return (explanation plus next N run times), validation failure behavior, and cost/auth model—everything an agent needs to call it correctly and interpret results.

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 each parameter is already documented. The description only restates defaults for count (5, max 20) and zone; it adds no syntax or edge-case detail for 'from' or expression aliases beyond what the schema provides, so baseline 3 applies.

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+resource ('Explain a standard 5-field cron expression') and specifies the outputs (plain-English explanation plus next N run times). It is clearly distinct from siblings like timezone_convert or holidays_business_days, which handle time but not cron parsing.

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?

Usage is implied by scope statements (supports lists, ranges, steps, macros; rejects invalid/never-firing expressions), but there are no explicit when-to-use/when-not conditions or named alternatives. The agent must infer that this is the cron-specific parser rather than a general time tool.

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