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

Annotations only declare read-only/idempotent/closed-world; the description goes well beyond by disclosing every modeling assumption baked into the numbers (15 días aguinaldo, 12 de vacaciones, 25% prima vacacional, prima de riesgo clase I, exclusión del impuesto estatal sobre nómina) and what the response contains. That is exactly the context an agent needs to decide whether the output is trustworthy for a given question.

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 the verb, scope and input basis, then assumptions, then the exclusions — a logical order with no filler. It is a single dense paragraph, though, and the assumption list could be scannable bullets rather than one long clause chain.

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, yet the description still tells the agent what comes back ('cifras mensuales y por periodo ... con desglose por concepto'), and the legal/assumption caveats plus the exclusion list cover the remaining ambiguity for a calculation tool with one required parameter.

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 carries mes, anio, periodicidad, zona_frontera_norte and the monthly-gross constraint. The description reinforces that the input is MENSUAL regardless of pay period and that periodicidad drives the ISR tarifa, but adds no syntax or edge-case detail beyond the structured fields, so the 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?

States a specific verb and resource (calcula la nómina de un trabajador asalariado en México) and enumerates exactly which components it computes: ISR Art. 96, subsidio al empleo, cuotas IMSS del trabajador y patronales, neto y costo patronal. It explicitly fences itself off from calcular_liquidacion / calcular_pension / honorarios / RESICO, so an agent can separate it from every sibling without opening a 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?

Gives a clear when-not boundary ('No sirve para honorarios, RESICO ni aguinaldo: sólo sueldos y salarios') plus the stipulations that make the result valid (prestaciones mínimas de ley, prima de riesgo clase I, sin percepciones extra, sin impuesto estatal). It does not name the sibling tool an agent should use instead for liquidaciones or pensiones, leaving that routing to inference.

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