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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds real behavioral context beyond that: the returned relations carry a publication date and official PDF link, and the `cobertura` field documents a genuine detection limitation (sole shareholders only, not partial stakes). That caveat is exactly the kind of non-obvious trait an agent could otherwise misread as complete ownership data.

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 definition is front-loaded: the resource and its two components come first, the cobertura caveat last. It is dense but every clause carries information (parent, subsidiaries, date, PDF, limitation). The first sentence is somewhat run-on, which keeps it short of a 5.

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 a 1-param, fully documented schema, an output schema, and readOnly annotations, this description covers purpose, return shape, and the main correctness caveat. The only meaningful gap is the absence of sibling routing (when to pick this over informe_completo or cuentas_anuales), which the description never addresses.

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?

There is a single parameter with 100% schema description coverage, and the schema itself already explains that empresa_id comes from asientouno_buscar_empresa. The description adds no format, range, or source detail for empresa_id, so the baseline 3 for a fully documented single-param schema is appropriate.

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 states a precise verb+resource: it returns the corporate group of a company per the BORME, split into matriz (sole-shareholder parent) and filiales (companies it sole-owns), each with date and official PDF. It also draws an explicit boundary ('solo detecta socios únicos, no participaciones parciales') that separates it from generic company-data siblings like asientouno_informe_completo.

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?

There is no explicit when-to-use or when-not-to-use guidance, nor any named alternative among the siblings (informe_completo, contratos_empresa, etc.). The link to asientouno_buscar_empresa for the id lives in the schema, not the description, so routing guidance is only inferable from the resource definition itself.

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