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

Annotations already declare the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds real value with two facts the structured fields do not carry: the tool accepts Spanish or English queries, and it returns document ids rather than full content (important since there is no output schema).

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?

Two sentences, both front-loaded: capability first, return/handoff second. The four examples are compact and each demonstrates a distinct query shape (relative date, location+date, conceptual, single term), so they earn their space rather than padding.

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?

For a one-parameter search with no output schema, the description covers input style, language coverage, and the shape of the return value plus the downstream tool. Minor gaps remain around result volume, ranking, and pagination behavior, but nothing that would cause a mis-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 coverage is 100% and the single parameter is documented as 'What to look for,' so baseline would be 3. The four inline query examples elevate this by showing the parameter is free-form natural language spanning dates, locations, single terms, and conceptual questions — meaning the schema alone would not convey.

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 (search) and resource (Quiniela Hoy results) scoped to natural-language queries, and the 'Returns document ids to pass to fetch' clause differentiates it from the retrieval siblings by positioning it as the entry point of a two-step flow. It stops short of naming which sibling it is *not* for (e.g. get_results for direct structured lookups).

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?

The 'document ids to pass to fetch' sentence gives clear workflow context — search first, fetch second — which is exactly the usage guidance an agent needs to chain these tools. There are no explicit exclusions or conditions telling the agent when to prefer get_results, get_number_info, or check_number instead.

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