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

Goes well beyond the readOnly/idempotent annotations: it names the model assumptions (single person 65+, no other income, combined approximate scale, art. 20 reduction not applied), pins the ruleset to 2026, states the response shape (opening line with the tupuente.es link, JSON starting with «url»), and requires a disclaimer plus source citation. No contradiction with annotations, which correctly mark this as a non-destructive, side-effect-free, closed-world read.

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?

Purpose is front-loaded and each clause carries real information (outputs, assumptions, link protocol, citation, usage criterion). It is a single dense block with a long parenthetical about the other tools' URL behavior that is useful but slightly tangles the front of the text; splitting into shorter sentences would improve scanability at no cost to content.

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 fully specifies the return contents (neto anual, neto mensual as anual ÷ 12, IRPF efectivo, supuestos, url) and the required presentation to the user. Assumptions, legal limits, and the advisory disclaimer are all present, leaving nothing an agent needs in order to call and report this correctly.

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 the schema already documents both parameters, their ranges, and the mutual exclusivity ("Usa esta o pension_bruta_anual, no las dos"). The description's "Indica la bruta anual o la mensual de cada una de las 14 pagas" restates that without adding syntax, units, or edge-case behavior, so baseline 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?

Opens with a specific verb and resource ("Pasa una pensión bruta a neta") and immediately lists the exact outputs: neto anual, neto al mes, IRPF efectivo y supuestos. It also anchors itself against the sibling calcular_pension by describing how that tool's "url" behaves with a pre-filled plan, so an agent can tell the two apart 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?

It states the input expectation ("Indica la bruta anual o la mensual de cada una de las 14 pagas") and the purpose (orientative calc vs. Seguridad Social report), which implies when to reach for it. However, there is no explicit routing rule against calcular_pension or the other siblings — the agent must infer that this is the net-from-gross converter rather than the full pension planner.

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