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

With no annotations, the description carries the full load, and it does disclose a real behavioral trait: a two-tier billing model (free approximate vs paid exact). That is more than the schema provides. However, it omits how the charge is triggered/authorized, what 'unverified' or 'incompleta' actually mean for a given request, and what happens when parameters are missing – significant gaps for a paid tool.

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 short sentences, front-loaded with the pricing dimensions before the cost caveat. Every clause carries information; the telegraphic noun-phrase style is tight rather than padded, though it reads more like a label than a full instruction.

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?

An 8-parameter pricing tool with no annotations and no output schema needs the description to explain return shape and input sufficiency, and it does neither. It never says what a response looks like, which parameters are needed for a valid quote, or what the free 'incompleta' result actually contains, so an agent must guess.

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 only 13% and 8 parameters are largely undocumented. The description names three concepts (región→ccaa, operador→operator, vehículo→vehicle) but adds no format, requiredness, or meaning for the remaining five (municipio, inspection, station_id, engine_cc, fuel). It does not compensate for the coverage gap as the low-coverage case requires.

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 states the resource and its axes explicitly: 'Tarifa por región, operador y vehículo' – an agent knows this returns ITV pricing keyed on those dimensions, which distinguishes it from cita_itv (booking) and periodicidad_itv (frequency). It stops short of a verb and never names the siblings it differs from, so it is clear but not fully differentiated.

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 explicit when-to-use or when-not-to-use versus buscar_estaciones or cita_itv. The one genuinely useful signal is the cost condition – free for unverified/incomplete data, $0.01 USDC only for an exact verified price – which implicitly tells the agent to weigh whether a paid exact quote is warranted, but the alternative (accept the free approximate value) is never framed as such.

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