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

Annotations already cover read-only and closed-world behavior, so the bar is lower. The description adds genuinely useful context beyond them: results are sorted by price ascending and the source is the ISP sanitary registry, which tells the agent what ordering to expect in the output. It stops short of stating whether prices are per pharmacy or aggregated.

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?

Three compact sentences with no filler; the ordering and source information is front-loaded before the value proposition and the disclaimer. The disclaimer is arguably marginal but is short and defensible in a health context.

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 single-parameter, no-output-schema lookup tool, the description covers what is returned, how it is ordered, and where the data comes from. It does not specify pagination or whether prices include pharmacy identity, but nothing critical for correct invocation 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% and there is a single parameter, so the schema already documents the argument including an example. The description adds nothing further about the active-ingredient string (e.g., accent handling, brand vs generic names). 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?

The description states a specific resource and result set: all brands containing a given active ingredient, ordered from cheapest to most expensive, sourced from the ISP registry. That is far more than a restatement of the name. It does not explicitly name its siblings (buscar_precio, ficha_medicamento), so sibling differentiation is only implicit.

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?

"Es donde está el ahorro grande: cambiar de marca rinde más que cambiar de farmacia" implies the scenario where this tool is preferable, giving a soft when-to-use signal. However, no alternative tool is named and no conditions for choosing between this and buscar_precio or ficha_medicamento are given. The closing line about not replacing medical advice is a safety disclaimer, not usage routing.

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