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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It reveals the accepted input formats (iso|unix) but says nothing about which parameters trigger which mode, what the diff result looks like, error behavior, or timezone handling.

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 fragment is short and front-loaded, but its brevity stems from under-specification rather than economy. Key operational details are absent when they should be present.

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?

A four-parameter tool with no annotations, no output schema, and zero parameter documentation is not described adequately. An agent has almost nothing to rely on to invoke it correctly.

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 0% across four parameters (a, b, date, days) and the description does not map any of them to operations. It only hints that date-style inputs are ISO or Unix, leaving the roles of a, b, and days entirely undocumented.

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 names three operations (parse/shift/diff) on dates, which is more than a tautology and roughly identifies the tool. However, it never clarifies how parse, shift, and diff relate to the four parameters, so an agent cannot tell exactly what a call will do. It is a vague but identifiable purpose.

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?

There is no guidance on when to use this versus the sibling 'time' tool or 'cron_next'. The '(iso|unix input)' note hints at accepted formats but gives no conditions for choosing this tool over alternatives.

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