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

Annotations already declare readOnly/openWorld=false/idempotent/non-destructive, so the safety profile is covered; the description adds value with determinism (same input, same output) and hard operational limits (64 KB input, 1 s per call, 1 MB result) that no annotation conveys. The "no stored state, no network" note partly restates annotations but reinforces the pure-function model. It does not discuss error behavior for invalid dates or oversized holiday lists.

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 purpose is front-loaded and every clause is substantive, but the content is delivered twice (ES and EN) and the English text is repeated again in the schema description, roughly tripling the reading cost. The "Not for" sentence also echoes the purpose verbatim before getting to the differentiator (Colombian holidays).

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?

Return values are covered by the output schema, and the description supplies the remaining pieces an agent needs: scope, sibling exclusion, determinism and resource limits. Only minor gaps remain (error semantics for malformed dates, whether holidays may fall on weekend days).

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 100%, with per-property descriptions for date, days, weekend (0=Sun…6=Sat, default [0,6]) and holidays (up to 2000 entries), so the schema already carries full parameter meaning. The description only broadens this to "configurable weekend days and given holidays" without adding format or interaction detail, which is the expected baseline-3 case.

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?

States a specific verb and resource (add/subtract N working days to a date) and immediately specifies scope: skips configurable weekend days and supplied holidays. It also names the sibling it is not (co-business-days-add with Colombian holidays), so an agent can separate the generic tool from the localized one without opening 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?

Explicit "When" clause ties use to contexts demanding exact calendar arithmetic (offset drift, DST, month ends, leap years), and a "Not for" clause points to co-business-days-add. It does not mention other adjacent siblings such as business-days-between or date-add, so routing is clear but not exhaustive.

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