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

Annotations already declare readOnlyHint/idempotentHint, so the safety profile is covered. The description adds real behavioral value by disclosing what it computes (days, weeks, months, hours) and that it works for past dates as well as future — information no annotation or output schema supplies.

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 sentences front-load the core question and the output metrics, with no filler. The trailing marketing URL is mildly wasteful but does not dilute the operative 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?

With no output schema, the description correctly sketches the return metrics, but it never clarifies how preset and target interact (e.g., that a custom preset requires an explicit target, or that target defaults to 2027-01-01). An agent could plausibly pass a target while leaving preset at its christmas default and get unexpected 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 coverage is 100%, so the preset, target, from and label semantics are fully documented in the schema, establishing a baseline of 3. The description reinforces the preset idea ('Christmas, New Year or your own date') but adds no syntax or precedence details beyond the schema.

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 states a specific computation (days/weeks/months/hours remaining) plus preset targets like Christmas and New Year, which distinguishes it from generic siblings such as date_difference_calculator. It does not explicitly name or contrast any sibling, so a 4 rather than a 5.

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 through examples ('until Christmas, New Year or your own date') and the note that it also handles dates already passed. However, there is no explicit when-to-use guidance versus close siblings like date_difference_calculator or ramadan_countdown_calculator, leaving the agent to infer the boundary.

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