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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint, destructiveHint=false). The description adds information annotations cannot carry: the unauthenticated quota behavior ('sin API key... hasta 10 resultados y un límite diario'), which affects how an agent should plan calls. It does not say what happens when the limit is hit or how pagination works, so it stops short of 5.

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?

Front-loaded with purpose, then usage conditions, alternatives, then quota caveat – a sensible priority order. The trailing English restatement is a minor redundancy that does not disrupt the flow.

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?

No output schema exists, and the description compensates by naming the returned fields (CIF, provincia, estado), so an agent knows what it can chain into get_company. Combined with the sibling routing and the quota note, nothing essential to calling this correctly is missing for a 2-parameter read tool.

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% with both parameters documented (query minLength 2, limit 1-25 default 10), so the baseline is 3. The description adds real meaning by explaining that the 10-result ceiling is the anonymous-mode cap while the schema's maximum of 25 is the authenticated ceiling. It adds no detail on matching behavior (accent handling, casing, partial word matching), which is the remaining gap.

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?

Specific verb + resource ('Busca empresas españolas por nombre o parte del nombre') plus the shape of what comes back (CIF, provincia, estado). It is clearly separable from get_company (needs a CIF) and find_cif_by_name (bulk resolution) without opening either schema.

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?

States the triggering condition explicitly ('Úsala cuando NO tienes el CIF'), the follow-up step ('después, get_company con el CIF elegido'), and names an alternative for a different case ('Para convertir una lista de muchos nombres en CIF, mejor find_cif_by_name'). When, when-not, and alternatives are all present.

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