Empresa por CIF

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

Beyond the readOnly/idempotent/openWorld annotations, the description discloses three things an agent cannot get from structured fields: the cost ('Gasta 1 consulta'), that certain returned fields are plan-gated (domicilio, tramo de facturación, ownership, GLEIF group, administradores), and the provenance/liability caveat that the status is derived by APIEmpresas from the BORME and is not a Registro Mercantil certificate.

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?

Purpose is front-loaded in the first clause, followed by the field list and the cost/caveat notes. The enumeration is dense but justified because no output schema exists, so the field list is the only return-value documentation; still, it runs long enough that a reader must scan the whole opening sentence.

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 so by enumerating fields, plan tiers, cost and data provenance. Remaining gaps are edge behavior (what happens for an unknown or malformed CIF) and nothing about response shape beyond the field list.

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% (both params documented with an example CIF and a plan note), so the baseline is 3. The description goes beyond it by tying include_directors to the concrete field it unlocks (administradores/cargos vigentes) and by listing which other fields depend on the plan, giving extra meaning over the schema text.

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 retrieval verb (fetch data for a Spanish company) plus the exact key it operates on (CIF/NIF), and enumerates the returned attributes. The 'by tax ID' framing implicitly separates it from name-based siblings such as search_companies and find_cif_by_name, and adds an English gloss for disambiguation.

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?

Usage is implied: call this when you already have a CIF/NIF and need company master data. It never explicitly names a sibling or states when NOT to use this tool (e.g. use verify_company to validate a CIF, search_companies when you only have a name). No exclusions or prerequisites beyond the plan note on optional fields.

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