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

readOnlyHint=true already tells the agent this is a safe, non-mutating computation. The description adds useful scope context — the applicable regime version (2025/2026) and that the flat rate for new autónomos is included — but says nothing about output format or edge cases. With annotations covering the safety profile, this is a modest but real addition.

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?

A single well-formed sentence with zero waste, front-loading the computed quantity (cuota mensual RETA) before the scope qualifiers. Every clause earns its place.

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 pure calculator with three fully-documented parameters and no output schema, the description conveys what is computed and under which regime. It could be marginally stronger by hinting at the return shape (a monthly amount in euros), but nothing essential to calling it correctly is missing.

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 fully documents regimen (with enum values and IRPF default), es_nuevo_autonomo and rendimiento_neto_mensual. The description's mention of the tarifa plana loosely maps to es_nuevo_autonomo but adds no syntax or format detail beyond the schema, 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 (Calcula), resource (cuota mensual de la Seguridad Social de un autónomo/RETA), and scope (sistema de cotización por rendimientos reales 2025/2026, más tarifa plana). This lets an agent distinguish it from siblings like calcular_gastos_deducibles_autonomo, calcular_modelo_130 or calcular_tarifa_freelance without opening the 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?

The description implies the context of use (self-employed workers under the real-income contribution system) but never states when to choose this over adjacent tools such as calcular_tarifa_freelance or comparar_autonomo_vs_sl, nor any exclusions. Usage is inferable but not explicit.

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