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

Adds substantial behavior beyond the annotations: data is company-level under Ley 37/2007 with no personal data, output is truncated to a 3-item sample without a Professional key, and the full listing is paywalled. The annotations only declare read-only/non-destructive/non-open-world; the description supplies the tiering and data-protection context an agent needs.

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?

Three tight sentences, front-loaded with the returned fields before the licensing caveat. The 'sin clave' condition is stated twice (once about keys, once about the 3-item sample), a minor redundancy.

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 does the necessary work of enumerating the returned statistics (count, average/median capital, monthly trend, provinces) and the access limitations. Nothing an agent needs to call it correctly is missing.

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% and the single parameter is fully documented (CNAE-2025 code, with or without dots). The description only restates that the code must be a CNAE-2025 code, adding no syntax, validation, or example detail beyond the schema, so the baseline of 3 applies.

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: returns company-incorporation statistics (count, capital, monthly trend, provinces) for a CNAE-2025 code. Very clear about what it produces, but never names or contrasts itself with closely related siblings such as detalle_cnae or subvenciones_por_actividad, so differentiation is left to inference.

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?

Gives concrete access conditions: no key needed for the statistics, a Professional key is required for the full list of recent incorporations (company names), and without a key a sample of 3 is returned. It stops short of stating when to prefer this tool over its CNAE-related siblings.

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