Parse a cron expression (paid via x402, $0.001)

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

With no annotations, the description carries the transparency burden. It discloses key behavioral traits: timezone support (any IANA), the computation of seconds until next, and that it is a pure computation (not an action trigger). It does not mention return format or errors, but for a simple compute tool the description is adequate and adds value beyond the schema.

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 core purpose. The second sentence introduces the alternative without excess wordiness. Every sentence earns its place, with no redundant or filler content.

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 and no annotations, the description gives a reasonable overview: it states the output type (next run times, seconds-until-next) and mentions timezone handling. It could be more explicit about the exact return structure (e.g., list of timestamps) and the cost (mentioned only in the title). However, the description is sufficiently complete for a moderate-complexity compute tool, especially with the clear sibling distinction.

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 only 33% (only cron is described). The description adds some parameter meaning by mentioning 'any IANA timezone' (for tz) and 'Next N' (for count), but it does not clarify defaults, ranges, or formats beyond what the schema already provides. It partially compensates but does not fully carry the burden for the undocumented 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 computes next N run times for a cron expression in any IANA timezone, plus seconds until the next run. It uses a specific verb-resource pairing and explicitly distinguishes itself from create_watch, which is a sibling tool for scheduling actions.

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: if the goal is for something to happen at the computed times, use create_watch with a schedule condition instead. This clearly states when not to use cron_next and names the alternative tool, fulfilling the when/when-not/alternatives requirement.

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