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

With no annotations, the description carries the full burden and does well: it discloses determinism, no network access, DST-aware behavior, and the x402 payment model. It omits error behavior for invalid expressions and whether 'from' defaults to now, which are the remaining gaps.

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?

Two dense sentences, fully front-loaded with the operation and its output before mentioning cost. Every clause carries information, and there is no filler.

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 correctly explains return values (local ISO, UTC ISO, epoch seconds) and the count range. It is close to complete, but the unexplained 'from' parameter and absence of error semantics for invalid expressions leave small gaps.

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 0%, so the description must compensate. It covers expr ('5-field cron expression'), tz ('any IANA time zone'), and count ('next 1-20 run times'), but the 'from' parameter is never explained or even referenced, and no format details for the date/time inputs are provided.

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 verbs (validate, return) applied to a concrete resource (5-field cron expression) with a quantified output (next 1-20 run times). It also enumerates supported syntax (lists, ranges, steps, JAN-DEC/SUN-SAT, @macros), which separates it cleanly from siblings like epoch_convert.

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 implies its use case (getting upcoming cron run times) but never states when to prefer it over alternatives such as epoch_convert, nor any exclusions or prerequisites. No explicit when-to-use guidance is given.

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