date_calc

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

Annotations already establish readOnlyHint, idempotentHint, and non-destructive behavior. The description adds substantial context beyond that: business-day defaults to Spain/Madrid, both ends counted, inclusion of public holidays, day-first numeric date parsing, Spanish month-name support, and the citation requirement. This is exactly the kind of behavioral nuance an agent needs.

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 long but well structured with a lead summary, per-operation bullets, a date-parsing note, and a keyword list. Some redundancy exists between the operation list and the keywords section, but every part adds operational value for a 17-parameter tool.

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?

Given high complexity, zero schema descriptions, and no output schema, the description is remarkably complete: it covers all operations, parameter meanings, defaults, date-format expectations, locale behavior, and trigger phrases. An agent can determine both when to invoke it and how to construct a correct call.

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%, so the description carries the full burden, and it succeeds. It maps every operation to its relevant parameters: diff uses start/end/unit, business_days uses start/end/include_end/country/subdivision, age uses birth_date/on, convert_tz uses value/from_tz/to_tz, and parse uses text. Even defaults and accepted formats are explained.

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 opens with a specific verb and resource: 'Date arithmetic', then enumerates the concrete operations (diff, add, business_days, weekday/iso_week, age, convert_tz, parse). This clearly separates date_calc from generic siblings like calc and math, and from units_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 gives strong contextual guidance through operation names and a keyword list ('how many days between', 'business days', 'deadline', 'zona horaria', etc.). It does not explicitly name sibling tools or say when not to use it, so it stops short of a 5.

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