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

Annotations already declare a safe read-only, closed-world operation. The description adds real behavioral context beyond them: it returns only a free-tier sample unless a payment plan applies, discloses 'Solo convocatorias públicas, sin datos personales', and notes 'Sin clave' (no API key required).

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?

Dense but front-loaded: the core purpose and return shape come first, then the paid-tier caveat and privacy note. Every clause carries information, though the single run-on sentence with parentheticals is slightly heavy.

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 well, enumerating total open grants, autónomo/PYME counts, and sample fields (título, órgano, ámbito, dotación, enlace oficial). Privacy and access requirements are also covered, leaving nothing essential for correct invocation.

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%, so both parameters are already documented in the schema. The description restates that 'code' is a CNAE-2025 and references the 'solo_actividad' filter, but adds no syntax or edge-case detail beyond what the schema provides. Baseline 3.

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 ('Devuelve') and resource ('subvenciones/ayudas públicas ABIERTAS (convocatorias BDNS)') scoped to a CNAE-2025 code. The subject matter clearly separates it from siblings like detalle_cnae or empresas_por_actividad, though it never names them 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?

Usage is implied by the input (query grants for a CNAE code), and the free-vs-paid split ('Con plan de pago: lista completa') hints at tiering, but there is no explicit when-to-use guidance or routing to alternatives. A note that this is the grant lookup for an activity code would raise it.

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