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

The description implies a read-only operation by stating it 'devuelve' (returns) data, but it does not explicitly declare idempotency, side effects, or authentication requirements. Since no annotations are provided, the description carries the full burden, and it lacks depth (e.g., rate limits, data freshness).

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 description is a single, clear sentence that conveys purpose and output without unnecessary words. It is well front-loaded and efficient.

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 simple retrieval tool with one parameter and no output schema, the description adequately states what is returned (data, status, tags, basic history). However, it could specify the structure of 'datos' or 'historial básico' to fully guide an agent.

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?

The input schema covers 100% of parameters with a description for 'email'. The description repeats the concept of searching by email but adds no new semantics (e.g., format expectations or validation). Baseline 3 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 specifies the action 'Busca' (searches) and the resource 'contacto' (subscriber) by email, with a clear list of returned data (datos, estado, etiquetas, historial básico). It distinguishes itself from siblings like create_subscriber, update_subscriber, and tag_subscribers by focusing on retrieval.

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?

No guidance is provided on when to use this tool instead of alternatives. The description does not mention preconditions, when to avoid it, or compare with similar tools like diagnose_deliverability or get_campaign_stats.

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