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

Annotations already establish read-only, open-world, and idempotent behavior. The description adds useful behavioral traits: it does not return the full stop list and it requires a search term. This goes beyond annotations, though the 'requiere nombre o línea' claim is not reflected in the schema's required fields.

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 sentences carry all essential information: search scope, output, downstream workflow, and a key limitation. There is no fluff or repetition of the schema.

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 tool without an output schema, the description helpfully states the return fields and workflow. However, the mismatch between the stated requirement ('nombre o línea') and the input schema (only network required) leaves an agent unsure how to construct a valid call. It also does not clarify how query and line interact when both are provided.

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 coverage is 100%, so the baseline is 3. The description adds some meaning by clarifying that query or line is the search key and that results include code, lines, and coordinates. However, it creates ambiguity by saying 'requiere nombre o línea' while the schema only marks network as required.

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 uses a specific verb ('Busca') and names a clear resource ('parada de autobús urbano o una estación de TRAM de Alicante'), plus the expected outputs ('código, líneas y coordenadas'). It also differentiates the tool from next_departures by explaining this is a prerequisite lookup step.

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 gives clear usage context: the agent should use this tool to find a stop by name or line, then call next_departures for upcoming departures. It also states a precondition, 'Requiere nombre o línea', but does not explicitly compare against sibling search tools like find_place or search_alicante.

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