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

Annotations already declare readOnlyHint, openWorldHint=false, idempotentHint and destructiveHint=false, so the restatement of 'no side effects' and 'deterministic' is largely redundant. However, the description adds genuinely new operational context not in annotations: 64 KB JSON input cap, 1 s per call, 1 MB result cap, and no stored state.

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?

Front-loaded with the action, then When / Not for / Side effects / Limits in a scannable order; every clause carries information. It loses a point because the full text is duplicated in Spanish and English, roughly doubling length for a single-locale caller.

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. The description still covers modes, exclusions, determinism and runtime limits, which is everything an agent needs to call this 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 coverage is 100%, so the baseline is 3, but the description adds meaning the schema does not: it explains the two modes and implicitly which parameters pair (date alone vs. week + iso_year). It still does not state what happens if all three are supplied or omitted (all params are optional), leaving the combination rules partly implicit.

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 ('Convierte una fecha a semana ISO 8601 ... o una semana ISO a su rango de fechas') and even covers the third behavior (reports weeks in an ISO year). It explicitly names the sibling it is not for (month-info), so an agent can distinguish it 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?

Provides an explicit 'Cuándo/When' trigger (exact date, time-zone or calendar results with offsets, DST, month ends, leap years) and an explicit 'No para/Not for' exclusion pointing at month-info. Both the positive selection condition and the alternative are named.

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