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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description is not obliged to restate it. It instead adds genuinely useful behavioral detail beyond annotations: a warning below 100 contracts, the first/last reliable year sentence, inclusion of source/period/read date, and null-with-reason for missing years.

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 content is front-loaded with the purpose, but the entire description is duplicated verbatim in Spanish and English, effectively doubling its length without adding information. Every sentence is relevant once, yet the bilingual repetition is pure redundancy for an agent consuming this definition.

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 carries the return-value burden and does it well: it specifies the units (€/month), contract counts, the <100-contract warning, the reliable-year sentence, provenance fields, and null semantics. Only the shape/ordering of the returned series is left implicit.

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 goes beyond the schema by explaining the semantic effect of omitting municipio (it lists towns with a sufficient series), which the schema only labels 'optional'. The language enum's default is already documented in 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 first sentence states a precise verb and resource: average rent of registered contracts per full year for one municipality, with the specific dataset cited (qww9-bvhh). It clearly distinguishes a per-year time series from what siblings like comparar_municipios or ficha_municipio would do, though it never names those alternatives explicitly.

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?

It discloses the fallback behavior when no municipality is supplied ('Without a municipality it lists the towns with a long enough series'), which implicitly tells the agent this tool doubles as a lister. However, it gives no explicit when-to-use versus-when-to-use-something-else guidance, and it does not route the agent to buscar_municipios or listar_municipios for that fallback case.

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