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

Annotations already declare readOnlyHint, idempotentHint and closed-world behavior, so the safety profile is covered. The description adds genuinely new context: a per-call price of $0.001 via x402, DST awareness, and the fact that country holidays are honored. It does not cover failure modes, such as what happens when both hours and end are supplied, or whether the 1-year window is an error.

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, both dense with signal: the computational scope first, then the pricing constraint. No filler or restatement of the title.

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?

An output schema exists, so return values need not be explained, and the cost note plus DST/holiday coverage handle the main complexity for a 10-parameter tool. The remaining gap is the mutual exclusivity of the two modes and how hours versus minutes combine, which an agent must deduce.

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?

With schema coverage at 50%, the description carries part of the load: it names business hours, custom hours, workdays, holidays and country public holidays, which maps to hours, work_start/work_end, workdays, holidays and country. However, minutes is never mentioned in the description and its relationship to hours is left ambiguous, and defaults (work_start 09:00, work_end 17:00, start = now) are only inferable from 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 precise domain and two concrete operations: the deadline N business hours after a start time, or business time elapsed between two times. That distinguishes it cleanly from calendar-based siblings such as date_add and from the overlap-oriented working_hours_overlap, without needing to open the schema.

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 usage through the two modes and the holiday/workday configuration, but it never states when to prefer it over date_add, date_diff, or working_hours_overlap, nor does it warn about the interaction of hours with a country code. The explicit mode selection ('pass hours/minutes' vs 'end') lives only in the schema description, not here.

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